The principal source of our knowledge of the holy angels is from Sacred Scripture. The angels are found in hundreds of citations in the Bible. Yet much teaching on the angels can also be found in the magisterial writings of the Church. Here we provide some of the more important sources for the Church's teaching on the angels.
327 The profession of faith of the Fourth Lateran Council affirms that God "from the beginning of time made at once (simul) out of nothing both orders of creatures, the spiritual and the corporeal, that is, the angelic and the earthly, and then the human creature, who as it were shares in both orders, being composed of spirit and body."
328 The existence of the spiritual, non-corporeal beings that Sacred Scripture usually calls "angels" is a truth of faith. The witness of Scripture is as clear as the unanimity of Tradition.
329 St. Augustine says: "'Angel' is the name of their office, not of their nature. If you seek the name of their nature, it is 'spirit'; if you seek the name of their office, it is 'angel': from what they are, 'spirit', from what they do, 'angel.'" With their whole beings the angels are servants and messengers of God. Because they "always behold the face of my Father who is in heaven" they are the "mighty ones who do His word, hearkening to the voice of His word".
330 As purely spiritual creatures angels have intelligence and will: they are personal and immortal creatures, surpassing in perfection all visible creatures, as the splendor of their glory bears witness.
331 Christ is the centre of the angelic world. They are His angels: "When the Son of man comes in His glory, and all the angels with Him..." (Mt 25:31). They belong to Him because they were created through and for Him: "for in Him all things were created in heaven and on earth, visible and invisible, whether thrones or dominions or principalities or authorities—all things were created through Him and for Him" (Col 1:16). They belong to Him still more because He has made them messengers of His saving plan: "Are they not all ministering spirits sent forth to serve, for the sake of those who are to obtain salvation?" (Heb 1:14).
332 Angels have been present since creation and throughout the history of salvation, announcing this salvation from afar or near and serving the accomplishment of the divine plan: they closed the earthly paradise; protected Lot; saved Hagar and her child; stayed Abraham's hand; communicated the law by their ministry; led the People of God; announced births and callings; and assisted the prophets, just to cite a few examples. Finally, the angel Gabriel announced the birth of the Precursor and that of Jesus Himself.
333 From the Incarnation to the Ascension, the life of the Word Incarnate is surrounded by the adoration and service of angels. When God "brings the firstborn into the world, He says: 'Let all God's angels worship Him'" (Heb 1:6). Their song of praise at the birth of Christ has not ceased resounding in the Church's praise: "Glory to God in the highest!" (Lk 2:14). They protect Jesus in His infancy, serve Him in the desert, strengthen Him in His agony in the garden, when He could have been saved by them from the hands of His enemies as Israel had been. Again, it is the angels who "evangelize" by proclaiming the Good News of Christ's Incarnation and Resurrection. They will be present at Christ's return, which they will announce, to serve at His judgement.
334 ...The whole life of the Church benefits from the mysterious and powerful help of angels.
335 In her Liturgy, the Church joins with the angels to adore the thrice-holy God. She invokes their assistance (in the Roman Canon's Supplices te rogamus... ["Almighty God, we pray that your angel..."]; in the funeral Liturgy's In Paradisum deducant te angeli... ["May the angels lead you into Paradise..."]). Moreover, in the "Cherubic Hymn" of the Byzantine Liturgy, she celebrates the memory of certain angels more particularly (St. Michael, St. Gabriel, St. Raphael, and the guardian angels).
336 From its beginning until death human life is surrounded by their watchful care and intercession. "Beside each believer stands an angel as protector and shepherd leading him to life" (St. Basil). Already here on earth the Christian life shares by faith in the blessed company of angels and men united in God.
In Brief: 350 Angels are spiritual creatures who glorify God without ceasing and who serve His saving plans for other creatures: "The angels work together for the benefit of us all" (St. Thomas Aquinas, STh I, 114, 3, ad 3).
351 The angels surround Christ their Lord. They serve Him especially in the accomplishment of His saving mission to men.
352 The Church venerates the angels who help her on her earthly pilgrimage and protect every human being.
391 Behind the disobedient choice of our first parents lurks a seductive voice, opposed to God, which makes them fall into death out of envy. Scripture and the Church's Tradition see in this being a fallen angel, called "Satan" or the "devil". The Church teaches that Satan was at first a good angel, made by God: "The devil and the other demons were indeed created naturally good by God, but they became evil by their own doing."
392 Scripture speaks of a sin of these angels. This "fall" consists in the free choice of these created spirits, who radically and irrevocably rejected God and His reign. We find a reflection of that rebellion in the tempter's words to our first parents: "You will be like God." The devil "has sinned from the beginning"; he is "a liar and the father of lies".
393 It is the irrevocable character of their choice, and not a defect in the infinite Divine Mercy, that makes the angels' sin unforgivable. "There is no repentance for the angels after their fall, just as there is no repentance for men after death."
394 Scripture witnesses to the disastrous influence of the one Jesus calls "a murderer from the beginning", who would even try to divert Jesus from the mission received from His Father. "The reason the Son of God appeared was to destroy the works of the devil." In its consequences the gravest of these works was the mendacious seduction that led man to disobey God.
395 The power of Satan is, nonetheless, not infinite. He is only a creature, powerful from the fact that he is pure spirit, but still a creature. He cannot prevent the building up of God's reign. Although Satan may act in the world out of hatred for God and His kingdom in Christ Jesus, and although his action may cause grave injuries—of a spiritual nature and, indirectly, even of a physical nature—to each man and to society, the action is permitted by Divine Providence which with strength and gentleness guides human and cosmic history. It is a great mystery that Providence should permit diabolical activity, but "we know that in everything God works for good with those who love him."