There is no direct reference to the use of the Sign of the Cross in worship in Sacred Scripture. Nevertheless, it would be highly presumptuous to denigrate this holy practice simply because of this fact, particularly as Scripture speaks so highly of the Cross as the instrument of our salvation: "May I never boast of anything except the cross of our Lord Jesus Christ ,by which the world has been crucified to me, and I to the world" (Gal.6, 14).

The Sign of the Cross is employed by the Church when it wishes to bestow the blessings of God on animate and inanimate creatures. It has also always been used as a means to mark out Christ's faithful. In this, it has its prefigurement in the Old Testament: "And the Lord said to him: Go through the midst of the city, through the midst of Jerusalem: and mark Thau upon the foreheads of the men that sigh, and mourn for all the abominations that are committed in the midst thereof...Utterly destroy old and young, maidens, children and women: but upon whomsoever you shall see Thau, kill him not, and begin ye at my sanctuary" (Ezek. 9, 4; 6). Thau is the last letter of the Hebrew alphabet and is in the form of a cross. From the very beginning, Christians have seen in the Thau a prefigurement of Christ's own Cross, and its application on people's foreheads, the Sign of the Cross.

Ezekiel 9, 4 has its echo in Rev. 7, 3: "Do not damage the earth or the sea or the trees, until we have marked the servants of our God with a seal on their foreheads." Can this seal be possibly any different from the "sign of the Son of man" (St. Matt. 24, 30) which is the Cross?

The early Christians were always eager to develop signs and symbols which summarized the great mysteries of the Faith. In the Sign of the Cross, two immense truths are signified together, namely the mystery of the Blessed Trinity: Father, Son and Holy Spirit, and the misery and humiliation of the Crucifixion. Spontaneously they drew this holy sign "on everything," accompanied by any one of the following words: "Sign of Christ"; "In the Name of Jesus"; "In the Name of the Father and of the Son and of the Holy Spirit" etc.

Constantine, before his great victory in the battle of Milvian Bridge(312 A.D.), which brought him to power as the first Christian Roman Emperor, saw in the sky a cross with the words "In Hoc Signo Vinces" - "in this sign you shall conquer." The victory of every Christian is achieved always through the power of the Cross. It was this sign that the Catholic armies defeated the Muslims at lepanto. The pope had asked that the Cross be displayed on all the ships' sails and that the prayers should be offered before battle . . . and the Christian fleet was victorious, and Europe saved from becoming Muslim.

Some quotes from the church Fathers :

Tertullian (c. 160-c. 225 AD):

"Your pearls' [including "signing"] are the distinctive marks of even your daily conversation. The more care you take to conceal them, the more liable to suspicion you will make them, and the more exposed to the grasp of Gentile curiosity. Shall you escape notice when you sign your bed, (or) your body; when you blow away some impurity; when even by night you rise to pray?" (To His Wife 5).

"We feel pained should any wine or bread, even though our own, be cast upon the ground. At every forward step and movement, at every going in and out, when we put on our clothes and shoes, when we bathe, when we sit at table, when we light the lamps, on couch, on seat, in all the ordinary actions of daily life, we trace upon the forehead the sign. For these and such like rules, if thou requires a law in the Scriptures, thou shalt find none: tradition will be pleaded to thee as originating, custom as confirming, and faith as observing them" (The Chaplet 3).

"The sick is visited, the indigent relieved, with freedom. Alms are given without danger of ensuing torment; sacrifices attended without scruple; daily diligence discharged without impediment: there is no stealthy signing, no trembling greeting, no mute benediction. Between the two echo psalms and hymns;[12] and they mutually challenge each other which shall better chant to their Lord. Such things when Christ sees and hears, He joys. To these He sends His own peace" (To His Wife 8).

Origen (c. 185-c. 284 AD):

"This (the letter Tau) bears a resemblance to the figure of the cross; and this prophecy (Ezek. ix. 4) is said to regard the sign made by Christians on the forehead, which all believers make whatsoever work they begin upon, and especially at the beginning of prayers, or of holy readings" (T. iii. Select. in Ezek. c. ix).

St. Hippolytus (c. 170-c. 236 AD):

"When she had done as he had directed her, she signed her whole body with the mystic sign (mystery) of the cross, and went forth from the place uncorrupted" (De Viq. Corinthiaca, t. ii).

St. Cyprian (d. 258 AD):

"The heading of chapter xxii. of the second Book of Testimonies is, "That in this sign of the cross is salvation to all who are marked on their foreheads."

"Ozias the king, when, bearing the censer, and contrary to God's law, with violence assuming to himself to sacrifice, despite the opposition of Azarias the priest, he refused to be obedient and to give way, was confounded by the wrath of God, was polluted by the spot of leprosy on his forehead, in that part of his body marked by his offended Lord, where they are signed who merit the Lord" (De Unitate).

Lactantius (c. 240-320 AD)

"Christ stretched out His hands death and measured the world; that even then He might show that, from the rising of the sun even to the going down of the same, a mighty people, assembled out of all tongues a tribes, would come under His wings, and receive on their for heads that greatest and sublime sign. [He then says that of this sign the marking of their door posts by the Jews, with the blood of the paschal lamb, was a type.] For Christ was a fair lamb without blemish, innocent, that is, and just and holy, who, sacrificed by those same Jews, is salvation to all who have marked the sign of blood, that is, who have marked on their foreheads the sign of the cross on which he shed his blood. . . . Let it suffice for the present to explain what is the potency of this sign. What a terror this sign is to devils He may know who sees how, when adjured through Christ, they flee from the bodies which they have obsessed. For as He, while living among men, put the devils to flight by a word, and restored to their former senses the troubled minds of those who had been driven to madness by their evil assaults, so now His followers expel those same foul spirits from men by the name of their master) and by the sign of His passion. Of this the proof is not difficult. For when they are sacrificing to their gods, if there stand by one who has his forehead signed, they cannot proceed with their sacrifices, And this has often been the chief cause why wicked kings have persecuted righteousness. For certain of ours, who were in attendance on their masters as they were sacrificing, by making the sign upon their foreheads, put to flight their gods, so that they could not describe what was to happen, in the bowels of the victims. . . . And as demons cannot come nigh unto those on whom they see the heavenly mark, nor hurt those whom the immortal sign fences round as an impregnable wall, they assail them by means of men, and persecute them by the hands of others" (Divin. Inst. c. 4, Oxon. n. 26-7).

Eusebius (c. 260-c. 340 AD):

"Eusebius narrates of Constantine that he was accustomed to "sign his countenance with the saving sign, and to glory in the victorious trophy" (De Vita Constant. 1. iii. e. 2).

St. Anthony (c. 251-356 AD):

"Neither ought we to fear these appearances (of evil spirits). For they are nothing, but quickly vanish, especially if one defend himself by faith and the sign of the cross" (Oratio ad Monachos, n. 8). This passage is quoted by St. Athanasius in his Life of St. Anthony, sec. 23. See also for similar mention of the use of the sign of the cross, in St. Anthony's Life, by St. Athanasius, p. 642; n. 35, p. 656; n. 53, p. 667; n. 80, p. 683.

St. Athanasius (c. 296-373 AD):

         "By the sign of the cross all magic ceases; all incantations are powerless; every idol is abandoned and deserted;           all irrational voluptuousness is quelled, and each one looks up from earth to heaven" (De Incarn. Verbi, t. I.).

St. Cyril of Jerusalem (c. 315-86 AD):

"Let us not, therefore, be ashamed of the cross of Christ, but even though another hide it do thou openly seal it on thy brow, that the devils beholding that royal sign may flee far away trembling. But make thou this sign when thou eatest and drinkest, sittest or liest down, risest up, speakest, walkest; in a word, on every occasion, for He who was here crucified is above in the heavens" (Catech. iv. n. 14).

"Many have been crucified throughout the world but none of these do the devils dread, but Christ having been crucified for us, when they see but the sign of the cross the devils shudder" (Catech, xii. n. 22).

"Let none be weary: take up arms against the adversaries in the cause of the cross itself: set up the faith of the cross as a trophy against the gainsayers. For when thou art about to dispute with unbelievers concerning the cross of Christ, first make with thy right hand the sign of the cross of Christ, and the gainsayer will be dumb. Be not ashamed to confess the cross" (Catech. xiii. n. 22).

"Let us not then be ashamed to confess the crucified. Let the cross become our seal, made with boldness by our fingers upon the forehead, oil every thing on the bread we eat, and the cups we drink; in our comings in and goings out; before sleep, when we lie down and when we awake; when we are walking and when we are still. Great is that preservative; it is gratuitous, for the poor's sake ; without toil for the sake of the weak ; since also its grace is from God; it is the sign of the faithful and the dread of devils. ­For He has triumphed over them in it, having exposed there confidently in open show (Colos. ii. 15). For when they see the cross they are reminded of the crucified: they are afraid of Him who has bruised the heads of the dragon. Do not despise the seal, because it is a free gift, but for this the rather honor the benefactor" (Catech. vi. n. 36).

St. Ephraem Syrus (c. 306-73 AD):

On Ezekiel 9:11: "And mark a sign upon the foreheads of the men that sigh, he says, for the circumcision of the flesh sufficed not unto salvation, and therefore has it been set aside, and the sign of the cross is substituted in its place" (T. ii. Syr. Comm. in Ezek).

"And having ended his prayer, as he withdrew, he thrice made the sign of the cross over the village" (T. ii. Gr. in Vit. S. Abra. v. T.).

"He signed himself with the cross, and thus addressed the evil spirit" (Ibid.).

"Let us crown our door­posts with the honored and life giving cross, saying with the Apostle, God forbid that I should glory, save in the cross of our Lord Jesus Christ (Gal. 4:14). Let us sign that same life­giving cross upon our door­posts, and on our foreheads, and on our breasts, and on our lips, and on every limb; and let us arm ourselves with this invincible weapon of Christians; the conqueror over death; the hope of the faithful; the light of the earth's boundaries; that opens paradise; that destroys heresies; faith's support ; the mighty safeguard, and salutary boast of the orthodox. This, O Christians, let us not cease, day and night, each hour and moment, to bear about us; without it do nothing; but in going to bed, and rising up, and working, and eating, and drinking, and journeying, and voyaging, and crossing rivers, adorn all your members with the life­giving cross, and there shall no evil come to thee, nor shall the scourge come near thy dwelling (Ps. 90:10). The adverse powers, on beholding this sign, depart trembling. This too has sanctified the world; this has dispelled darkness, and brought back light; this has destroyed error; this from the sun's rising to its setting, and from north to south, has gathered together the nations, and linked them in love into one Church, one faith, and one baptism. This is the impregnable wall of the Orthodox. What mouth, or what tongue, shall worthily sing the praises of the invincible weapon of Christ the king? . . . And this and more than this (might be) said concerning the honored cross" (T iii. Gr. in Secund. Adv. Dom.)

St. Gregory of Nyssa (c. 330-c. 395 AD):

"In the dying address of St. Macrina we find the following: "Thou, O God, hast given unto those that fear Thee a sign, the form of Thy holy cross, for the destruction of the adversary, and for the safeguard of our life' . . . And at the same time that she was speaking these words she formed (laid) upon her eyes and mouth, and heart the sign (or seal)" (T. ii. De Vita S. Macrinae).

"Having entered the temple with his attendants, he (St. Greg. Thaum.) at once filled with dread the evil spirits, by invoking the name of Christ; and with the sign of the cross be purified the air defiled with vapors" (T. iii. De Tita S. Greg.).

"Let the sheep hasten unto the seal (character) and that sign of the cross which is a remedy against evils" (T. iii. App. De Baptismo).

St. Gregory of Nazianzum (329-89 AD):

"But when, as this man (Julian) proceeded in his career, fears began to assail him, he flies unto the cross, and to his old remedy, and with this he signs himself against his terrors, and Him whom he bad persecuted he makes his helper. And what follows is more fearful. The sign of the cross prevailed; the demons are vanquished; his fears cease; and then? He again breathes forth evil; he recovers his audacity; he dares again; and again the same fears, and again the sign of the cross, and the quiescent demons" (Contr. Julian. Orat. iii. T. I.). For the custom of blessing bread with the sign of the cross, see T. I. Orat. xix.

"Avaunt, demons lest I smite thee with the cross; the cross before which all things tremble. I bear the cross upon my limbs; the cross accompanies me on my journeyings; the cross is my heart; the cross is my glory" (T ii. Carm. xxi).

St. Basil (c. 330-79 AD):

        "Gordius having thus spoken and signed himself with the sign of the cross, advanced to receive the stroke"            (Hom. in Gord. Mart. T. ii. P. I. n. 81).

St. Macarius of Egypt (c. 300-c. 390 AD):

         "After the sign of the cross, grace immediately thus operates, and composes all the members and the heart, so that             the soul from its abounding gladness seems as a youth that knows not evil" (Rom. ix. p. 481).

St. Epiphanius (c. 315-403 AD):

He says of a woman exposed to sin that she signed herself in the name of Christ; for she was Christian. [He then  mentions recourse being had to magic to seduce her, and observes:] This was the third circumstance that taught him  that the power of magic availed not against the name of Christ, and the sign (seal) of the cross" (T I. Adv.Haeres.) He also mentions a case of madness described as being cured by the sign of the cross.

St. Ambrose (c. 339-397 AD):

"But now there is no need of the slight pain of circumcision for a Christian people, which bearing about the death of the Lord, inscribes at every instant, upon its own forehead, the contempt of death as knowing that it cannot have salvation without the cross of the Lord" (T iii. Ep. lxxi. Constanzo, n. 12).

"The catechumen believes also in the cross of our Lord Jesus, with which (cross) also he is signed" (T. ii. de Xyster. e. iv. n. 20).

Nilus the Ascetic (d. c. 430 AD):

"Certain Christians whilst seeking for the bodies of some who had been martyred, were terrified, and each of them impressed the sign of the cross upon their foreheads, when there appeared to them a brilliant cross which they seemed to see emit a flash of fire from the eastern side; and they immediately bent the knee to pray towards the place where the cross appeared to them" (Martyr, St. Theodot. Ancyr. n. 17).

"When he had said this, Theodotus made the sign of the cross over his whole body, and proceeded, without turning to the stadium" (Ibid. n. 21).

St. Jerome (c. 342-420 AD):

"Let the banner of the cross be planted on thy forehead's" (T. I. Ep. xiv. ad fleliod. n. 6).

"At every action, at every step, let thy hand depict the cross of the Lord" (Ib. Ep. 23).

"To enter into a Church that is not the mark of a true Christian, seeing that many unworthy person enter with us, nor the making the sign of the cross" (Galland. T. vii.) 529.

"Keep the door of your heart shut, and frequently defend your forehead with the sign (seal) of the cross, lest the exterminator of Egypt find some (unguarded) spot in you" (Ep. cxxx. n. 9).

St. Chrysostom (c. 347-407 AD):

"And how wilt thou enter into the (Jewish) synagogue ? For if thou shalt sign thy forehead, instantly will the wicked power that dwells in that synagogue flee away; but if thou sign not thyself, thou wilt at once, at the very doors, have flung away thy weapons; and then the devil, taking thee naked and weaponless, will load thee with ten thousand evils" (T. I. Or. viii. Adv. Jud. n. 8).

Reflect why the whole world hastens to look, upon a grave that now contains no body: what power draws men from the very extremities of the earth, to gaze on where He was born, where buried, where crucified. Contemplate the cross itself, what a sign of power it is. For that cross was previously an accursed thing, a shameful death; yea a death of all others the most disgraceful. But lo! now it has become more honored than life ; more resplendent than diadems; and we all bear it about on our foreheads not merely not ashamed of it but even glorying in it. Not private individuals only, but even they that wear the diadem, bear it on their foreheads in preference to that diadem: and justly. For better is that than countless diadems. For the diadem adorns indeed the brow, but the cross protects the mind. This is that which repels demons; this the diadem that removes the soul's diseases; this an invincible weapon; this an impregnable wall; this an unconquerable safeguard; this not only repels the irruptions of barbarians and the incursions of hostile troops, but the phalanxes of pitiless demons" (T. v. Expos. in Ps. cix. n. 6).

"Wherefore let no one be ashamed of the venerable symbols of our salvation, and of the chiefest of good things, whereby also we live, and whereby we are; but as a crown so let us bear about the cross of Christ. For indeed by it all things are perfected amongst us: whether one is to be regenerated the cross is there; or to be nourished with that mystic food; or to be ordained; or to do anything else soever, everywhere this our symbol of victory is present. For this cause, both on house, and walls and doors, and on the forehead and on the mind, do we inscribe it with much care. For of the salvation wrought for us; and of the common freedom; and of the goodness of our Lord ; this is the sign. For, >as a sheep was He led to the slaughter'. Whensoever, therefor thou signest thyself, reflect on the whole purport of the cross, and quench anger and all the other passions. When thou signest thyself, fill thy forehead with great confidence; make thy soul free. . . . For not merely are we to engrave it with the finger; but before this, with the will with much faith. If thou shalt thus fashion it on thy face, none of the unclean demons will be able to come near thee, seeing the blade from which he received his wound, seeing the sword from which he had his mortal wound. . . . This is the sign which for our forefathers and for as has opened closed doors; this has quenched poisonous drugs; this has taken away the power hemlock; this has healed the bites of venomous beasts" (T. vii. liv. in Matt. n. 4).
"If you perceive thy heart burning within you, seal thy breast placing on it the cross" (Ib. Hom. 87 n. 2).

St. Augustine (354-430 AD):

"What is the sign (or seal) of Christ, but the cross of Christ? Which sign, unless it be applied, whether to the foreheads of believers, or to the water itself whereby they are regenerated, or to the oil wherewith they are anointed with chrism, or to the sacrifice by which they are fed, none of these things is rightly performed. How then can it be, that by that which the wicked do no good thing is signified, when by the cross of Christ, which the wicked made, every good thing is signified to us in the celebration of His sacraments" (T. iii. Tract. cxviii. in Toan. n. 5).

"Not without cause did Christ wish His sign to be impressed upon our foreheads, on the seat as it were of shame, lest the Christian might blush at the indignities offered to Christ" (T.iv. in P8. xxx. Serm. iii. n. 7).

"Whatsoever thou mayest suffer, thou wilt not approach those insults, those scourgings, that disgraceful robe, that thorny crown; thou wilt not, in fine, come to that cross, because now it has been removed as a punishment by the Human race. For whereas, under those of old, criminals were crucified, now no one is crucified. It was honored and ceased. It ceased as a punishment, it remains as a glory. From the places of punishments it has passed to the foreheads of emperors" (T. iv. in P8. xxxvi. Serm. 2).

Sulpicius Severus (c. 360-c. 420 AD):

"He (St. Martin of Tours) having lifted on high the sign of the cross upon those who were opposite to him, and commanded the crowd not to stir, but to lay down their burdens then might be seen those miserable men in a wonderful manner grow rigid as stones" (Galland t.viii. De ViN.B. Xartini, n. 12).

"Against the (visible assaults of the) devil he always protected himself by the sign of the cross and the help of prayer" (R. n. 22).

"Worshipper of God, remember that thou hast, under the hallowed dew of the font and of the laver, been signed with chrism. Let, when sleep summons thee to thy chaste couch, the sign of the cross be imprinted on thy forehead, and on thy heart. The cross drives far away all crime; darkness flees before it; the mind consecrated by that sign cannot fluctuate" (Lib. Hymn. 6 per horas, Ente Somnum).

St. Maximus (d. 408/23 AD):

"When we rise in the morning we ought to give thanks to God, and to do every action throughout the day in the sign of the Savior. While thou wast yet a Gentile, was it not thy custom to seek for signs, and to ascertain with great care what signs were favorable to certain things? Now I would not have thee be mistaken in their number; know then that, in the one sign of Christ there lies undoubted success in ever thing. He who, in this sign, begins to sow, will reap as fruit life everlasting; he who in this sign begins his journey, will reach heaven in this name, therefore, are all our actions to be regulated" (Homily ii. De Non Timendis Hostibus).

Paulus Orosius (d. c. 380 AD):

"Theodosius narrowing himself without friends, but that he was surrounded by enemies, with his body prostrate on the earth, but his mind fixed on heaven, prayed alone to Christ alone, who is able to do all things. Having spent a sleepless night in uninterrupted prayer . . . he confidently, though alone, seized his weapons, conscious that he was not only to be protected by the sign of the cross, but thereby even to be victorious; fortifying himself with that sign, he gave the signal for battle" (Histor l. vii. c. 55).

St. Cyril of Alexandria (c. 315-86 AD):

Explaining Is. xix. 19: "He, in this place, calls the sign of the holy cross, with which it is the custom of believers to be fenced round, a pillar. For this we have ever used ; overthrowing every assault of the devil, and repelling the attacks of evil spirits. For an impregnable wall is the cross unto us, and our glorying in it is truly salutary. God forbid that I should glory, save in the cross of Christ" (T. I Comm. in.Isa. lib. ii).

Theodoret (c. 393-c. 466 AD):

Having narrated a miracle performed by St. James of Nisibis, he says: "Such was the miracle performed by this new Moses, effected not by a stroke with a rod, but a power manifested by the sign of the cross" (T iii. Relig. e. I. p. 1111.). For other miracles ascribed to the same cause, see Ibid. e. ii. p. 1125; e. iii. p. 1140; c. viii.).

The well-known account of Julian, after his apostasy, using inadvertently the sign of the cross, when under terror front evil spirits, is found also in Theodoret See also in that same history the account of a miracle ascribed to water blessed by the sign of the cross. "All Christians honor the sign of the cross" (T. iv. Or. vi. De Prov.)

Pope St. Leo I (d. 461 AD):

"The sign of the cross makes all who have been regenerated in Christ kings, but the unction of the Holy Spirit consecrates priests" (T. I. Serm. iv. in Natal. Ordin. c. I).

"They who are ashamed to proclaim with the lips what they have received to be borne on their foreheads, will show that they have derived no virtue from the sign of the cross" (Ep. cxxiv. ad Monackos Palcestinos, c. viii).