Angels Who Are Also Saints
Q: In another question you mention those saints who are angels. Do you mean angels (who are also called saints), or do you mean saints who have gone before us to heaven who are now angels? I have often heard of people calling someone who has died an angel. Is this Catholic belief?
A: Definitely not. Any such references are purely poetic.
Humans and angels are two different orders of beings. By their natures, humans are both physical and spiritual, but angels are only spiritual. One may express this by saying that while humans have rational spirits, angels are rational spirits.
This basic nature never changes, even when humans are temporarily deprived of their bodies by death. Their nature is still such that, in order to be completed beings, they must have bodies. Thus the final destiny of humans is to return to physical form in resurrection, while the final destiny of angels is to remain in unembodied spiritual form forever.
Thus the Catechism of the Catholic Church states:
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.
Who are they?
329 St. Augustine says: “‘Angel [i.e., “messenger”]’ 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'” [St. Augustine, En. in Ps. 103, 1, 15: PL 37, 1348]. 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” [Mt 18:10; Ps 103:20].
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 [Cf. Pius XII, Humani generis DS 3891; Lk 20:36; Dan 10:9- 12].