The most usual form in which good angels appear, both in the Old Testament and the New, is the human form. It was in that shape they showed themselves to Abraham, Lot, Jacob, Moses, Joshua, Manoah the father of Samson, to David, Tobit, the Prophets; and in the New Testament they appeared in the same form to the Holy Virgin, to Zachariah the father of John the Baptist, to Jesus Christ after his fast of forty days, and to him again in his agony in the Garden of Olives. They showed themselves in the same form to the holy women after the resurrection of the Savior. The one who appeared to Joshua on the plain of Jericho appeared apparently in the guise of a warrior, since Joshua asks him, "Art thou for us, or for our adversaries?"
Sometimes they hide themselves under some form which has resemblance to the human shape, like who appeared to Moses in the burning bush, and who led the Israelites in the desert in the form of a cloud, dense and dark during the day, but luminous at night. The Psalmist tells us that God makes his angels serve as a piercing wind and a burning fire, to execute his orders.
The cherubim, so often spoken of in the Scripture, and who are described as serving for a throne to the majesty of God, were hieroglyphical figures, something like the sphinx of the Egyptians; those which are described in Ezekiel are like animals composed of the figure of a man, having the wings of an eagle, the feet of an ox; their heads were composed of the face of a man, an ox, a lion, and an eagle, two of their wings were spread towards their fellows, and two others covered their body; they were brilliant as burning coals, as lighted lamps, as the fiery heavens when they send forth the lighting's flash -- they were terrible to look upon.
The one who appeared to Daniel was different from those we have just described; he was in the shape of a man, covered with a linen garment, and round his loins a girdle of very fine gold; his body was shining as a chrysolite, his face as a flash of lightning; his darted fire like a lamp; his arms and all the lower part of his body was like brass melted in the furnace; his voice was loud as that of a multitude of people.
St. John, in the Apocalypse, saw around the throne of the Most High four animals which doubtless were four angel; they were covered with eyes before and behind. The first resembled a lion; the second an ox; the third had the form of a men; and the fourth was like an eagle with outspread wings; each of them had six wings, and they never ceased to cry night and day, "Holy, holy, holy, Lord God Almighty, who was, and is, and is to come."
The angel who was placed at the entrance of the terrestrial paradise was armed with a shining sword, as well as the one who appeared to Balaam, and who threatened, or was near killing both himself and his ass; and so, apparently, was the one who showed himself to Joshua in the plain of Jericho, and the angel who appeared to David, ready to smite all Israel. The angel Raphael guided the young Tobias to Rages under the human form of a traveler. The angel who was seen by the holy woman at the sepulchre of the Savior, who overthrew the large stone which closed the mouth of the tomb, and who was seated upon it, had a countenance which shone like lightning, and garments white as snow.
In the Acts of the Apostles, the angel who extricated them from prison, and told them to go boldly and preach Jesus Christ in the temple, also appeared to them in a human form. The manner in which he delivered them from the dungeon is quite miraculous; for the chief priests having commanded that they should appear before found the dungeon empty. How could an angel without opening, or any fracture of the doors, thus extricate men from prison without either the guards or the jailer perceiving anything of the matter? The thing is beyond any known powers of nature; but it is no more impossible than to see our Saviour, after his resurrection, invested with flesh and bones, as he himself says, come forth from his sepulchre, without opening it, and without breaking the seals, enter the chamber wherein were the apostles without opening the doors, and speak to the disciples going to Emmaus without making himself known to them; then, after having opened their eyes, disappear and become invisible. During the forty days that he remained upon earth till his ascension, he drank and ate with them, he spoke to them, he appeared to them; but he showed himself only to those witnesses who were pre-ordained by the eternal Father to bear testimony to his resurrection.
The angel who appeared to the centurion Cornelius, a pagan, but fearing God, answered his questions, and discovered to him unknown things, which things came to pass.
Sometimes the angels, without assuming any visible shape, give proofs of their presence by intelligible voices, by inspirations, by sensible effects, by dreams, or by revelations of things unknown, whether future or past, sometimes by striking with blindness, or infusing a spirit of uncertainty or stupidity in the minds of those whom God wills should face the effects of his wrath; for instance, it is said in the Scriptures that the Israelites heard no distinct speech, and beheld no form on Horeb when God spoke to Moses and gave him the Law.
The angel who might have killed Balaam's ass was not at first perceived by the prophet; Daniel was the only one who beheld the angel Gabriel, who revealed to him the mystery of the great empires which were to succeed each other.
When the Lord spoke for the first time to Samuel, and predicted to him the evils which he would inflict on the family of the high-priest Eli, the young prophet saw no visible form; he only heard a voice, which he at first mistook for that of the high-priest Eli, not being yet accustomed to distinguish the voice of God from that of a man.
The angels who guided Lot and his family from Sodom and Gomorrah were at first perceived under a human form by the inhabitants of the city; but afterwards these same angels struck the men with blindness, and thus prevented them from finding the door of Lot's house, into which they would have entered by force.
Thus, then, angels do not always appear under a visible or sensible form, nor in a figure uniformly the same; but they give proofs of their presence by an infinity of different ways -- by inspirations, by voices, by prodigies, by miraculous effects, by predictions of the future, and other things hidden and impenetrable to the human mind.
St. Cyprian relates that an African bishop, falling ill during the persecution, earnestly requested to have the viaticum administered to him; at the same time he saw, as it were, a young man, with a majestic air, and shining with such extraordinary lustre that the eyes of mortals could not have beheld him without terror; nevertheless, the bishop was not alarmed. This angel said to him, angrily, and in a menacing tone, "You fear to suffer. You do not wish to leave this world. What would you have me do for you?" (or "What can I do for you?") The good bishop comprehended that these words alike regarded him and the other Christians who feared persecution and death. The bishop talked to them, encouraged them, and exhorted them to arm themselves with patience to support the tortures with which they were threatened. He received the communion, and died in peace. We shall find in different histories an infinite number of other apparitions of angels under a human form.
This article is from Augustine Calmet's book called The Phantom World: The History and
Philosophy of Spirits, Apparitions, etc, etc.
Good angels of the Old Testament
Good angels in the New Testament
Appearance of good angels
Opinions concerning good angels
Apparitions of good genii
Objections to the reality of magic
Reply to objections to the reality of magic
Examination of the affair of Hocque, magician
Magic of the Egyptians and Chaldeans
Magic among the Greeks and Romans
Examples which prove the reality of magic