It is the mind of the Church that every individual person has allotted to them a Guardian Angel by God. It is clear from both the Old and New Testaments that angels are God's ministers who carry out His will, and at appointed times are allotted special commissions to intervene in the affairs of mankind.
The lowest choirs of angels are sent to us as guardians. Guardian Angels, they can act upon our senses and our imaginations, and through these same faculties upon our wills. Not only the baptized, but every person, including children, receives a Guardian Angel, who remains with us even in heaven.
In the Sacred Scripture, the doctrine of Guardian Angels is given no special consideration, but rather is taken for granted:
"The two angels came to Sodom in the evening, and Lot was sitting in the gateway of Sodom. When Lot saw them, he rose to meet them, and bowed down with his face to the ground... When morning dawned, the angels urged Lot, saying, Get up, take your wife and your two daughters who are here, or else you will be consumed in the punishment of the city" (Gen. 19,1-15);
"But now go, lead the people to the place about which I have spoken to you; see, my angel shall go in front of you. Nevertheless, when the day comes for punishment, I will punish them for their sin" (Exod.32, 34);
"At that time the prayers of them both were heard in the sight of the glory of the most high God: And the holy angel of the Lord, Raphael was sent to heal them both, whose prayers at one time were rehearsed in the sight of the Lord" (Tob. 3, 24-25 [Douai]);
"For he will command his angels concerning you to guard you in all your ways" (Ps. 91, 11);
"But the prince (angel) of the kingdom of Persia opposed me twenty-one days. So Michael, one of the chief princes, came to help me, and I left him there with the prince of the kingdom of Persia, and have come to help you understand what is to happen to your people at the end of days. For there is a further vision for those days...But I am to tell you what is inscribed in the book of truth. There is no one with me who contends against these princes except Michael, your prince" (Dan. 10, 13-14; 21);
"When Maccabeus and his men got word that Lysias was besieging the strongholds, they and all the people, with lamentations and tears, prayed the Lord to send a good angel to save Israel" (2 Macc. 11, 6).
In the New Testament the doctrine of Guardian Angels is stated more precisely:
"Take care that you do not despise one of these little ones; for, I tell you, in heaven their angels continually see the face of my Father in heaven" (St. Matt. 18, 10);
"Then the high priest took action; he and all who were with him (that is, the sect of the Sadducees), being filled with jealousy, arrested the apostles and put them in the public prison. But during the night an angel of the Lord opened the prison doors, brought them out, and said, Go, stand in the temple and tell the people the whole message about this life" (Acts 5, 17-20);
"Then Peter came to himself and said, Now I am sure that the Lord has sent his angel and rescued me from the hands of Herod and from all that the Jewish people were expecting. As soon as he realized this, he went to the house of Mary, the mother of John whose other name was Mark, where many had gathered and were praying. When he knocked at the outer gate, a maid named Rhoda came to answer. On recognizing Peter's voice, she was so overjoyed that, instead of opening the gate, she ran in and announced that Peter was standing at the gate. They said to her, You are out of your mind! But she insisted that it was so. They said, It is his angel" (Acts 12, 11-15);
"Are not all angels spirits in the divine service, sent to serve for the sake of those who are to inherit salvation?" (Heb. 1, 14).
St. Michael was the special protector of Israel and is now invoked as the guardian of the Christian faithful against the wickedness and snares of Satan. How we should love our Guardian Angels and invoke their aid in all the circumstances of our lives.
Some quotes from the Church Fathers:
The Shepherd of Hermas (C. 140-155 A.D.): "God planted the vineyard," (the shepherd) said: "that is, He created the people, and gave them over to His Son. And the Son appointed the angels to guard over them; and He Himself cleansed them of their sins, labouring much and undergoing much toil."
St. Clement of Alexandria, Miscellanies (Post 202 A.D.): "The thoughts of virtuous men are produced by divine inspiration. The soul is disposed in the way it is, and the will of God is conveyed to human souls, by special divine ministers who assist in such service. For regiments of angels are distributed over nations and cities; and perhaps some even are assigned to particular individuals."
Origen, Homilies on Luke (Post 233 A.D.): "To every man thereare two attending angels, the one of justice and the other of wickedness.If there be good thoughts in our heart, and if righteousness be wellingup in our soul, it can scarcely be doubted that an angel of the Lord isspeaking to us. If, however, the thoughts of our heart be turned to evil,an angel of the Devil is speaking to us."
St. Basil the Great, Against Eunomius (Inter 363-365 A.D.): "Allthe angels, having but one appellation, have likewise among themselvesthe same nature, even though some of them are set over nations, while othersof them are guardians to each one of the faithful."