Isaias 63:9

4. Again, that it should not be a mere man who should save us, nor [one] without flesh, for the angels are without flesh, [the same prophet] announced, saying: “Neither an elder, nor angel, but the Lord Himself will save them because He loves them, and will spare them: He will Himself set them free.” And that He should Himself become very man, visible, when He should be the Word giving salvation, Isaiah again says: “Behold, city of Zion: thine eyes shall see our salvation.” And that it was not a mere man who died for us, Isaiah says: “And the holy Lord remembered His dead Israel, who had slept in the land of sepulture; and He came down to preach His salvation to them, that He might save them.” And Amos (Micah) the prophet declares the same: “He will turn again, and will have compassion upon us: He will destroy our iniquities, and will cast our sins into the depths of the sea.” And again, …

But Christ, they say, bare (the nature of) an angel. For what reason? The same which induced Him to become man? Christ, then, was actuated by the motive which led Him to take human nature. Man’s salvation was the motive, the restoration of that which had perished. Man had perished; his recovery had become necessary. No such cause, however, existed for Christ’s taking on Him the nature of angels. For although there is assigned to angels also perdition in “the fire prepared for the devil and his angels,” yet a restoration is never promised to them. No charge about the salvation of angels did Christ ever receive from the Father; and that which the Father neither promised nor commanded, Christ could not have undertaken. …

In Isaiah: “Be comforted, ye weakened hands; and ye weak knees, be strengthened. Ye who are of a timorous heart, fear not. Our God will recompense judgment, He Himself will come, and will save us. Then shall be opened the eyes of the blind, and the ears of the deaf shall hear. Then the lame man shall leap as a stag, and the tongue of the dumb shall be intelligible; because in the wilderness the water is broken forth, and the stream in the thirsty land.” Also in that place: “Not an elder nor an angel, but the Lord Himself shall deliver them; because He shall love them, and shall spare them, and He Himself shall redeem them.” Also in the same place: “I the Lord God have called Thee in righteousness, that I may hold Thine hand, and I will comfort Thee; and I have given Thee for a covenant of my people, for a light of the nations; to open the eyes of the blind, to bring forth them that are b …

VI. But let us, beloved, return in our discourse to that point whence we digressed, exclaiming, Blessed is He that cometh in the name of the Lord: that good and kind Shepherd, voluntarily to lay down His life for His sheep. That just as hunters take by a sheep the wolves that devour sheep, even so the Chief Shepherd, offering Himself as man to the spiritual wolves and those who destroy the soul, may make His prey of the destroyers by means of that Adam who was once preyed on by them. Blessed is He that cometh in the name of the Lord: God against the devil; not manifestly in His might, which cannot be looked on, but in the weakness of the flesh, to bind the strong man that is against us. …