​‘How can we make a fitting recompense for so great a condescension? The one only-begotten God, born of God in an unutterable way, is enclosed in the shape of a tiny human embryo in the womb of the Virgin and grows in size. He who contains all things and in whom and through whom everything came into existence is brought forth according to the law of human birth; and he at whose voice archangels tremble, and the heavens, the earth and all the elements of the world dissolve is heard in the cries of a baby. He who is invisible and incomprehensible and is not to be judged by estimates of sight, sense and touch, is covered up in a cradle. If anyone considers these conditions unfitting for a God, he will have to admit that his indebtedness to such generosity is all the greater, the less they are suited to the majesty of God.
 
It was not necessary for him through whom man was made to become man, but it was necessary for us that God should be made flesh and dwell with us, that is to say, dwell within all flesh by assuming one fleshly body. His abasement is our glory. What he is, while appearing in the flesh, that we have in turn become: restored to God’.
 
St Hilary of Poitiers, c.315-367

‘Thou, O man, hast two enemies, sin and death, that is to say, the death of the soul and the death of the body. Christ is come to conquer both, and from both will He save thee. Only be not afraid. Even already He has vanquished sin in His own Person by taking upon Himself our human nature, free from all defilement. For great violence was done to sin, and it manifestly sustained a heavy defeat, when that very nature which it boasted of having entirely corrupted and completely subdued, was found in Christ wholly reclaimed from it. After this first victory, He “will pursue after (thy) enemies and overtake them, and (He) will not turn back again till they are consumed”. Fighting against sin during His mortal existence, He will oppose it with His words and example; in His passion He will bind it, He will bind “the strong man and plunder his house”. Then, as regards death, He will in the same manner and order vanquish it first in Himself, when He rises from the tomb, “the first-fruits of them that sleep... the First-Begotten of the dead”. Afterwards He will overcome it in us also, when He will raise up again our mortal bodies: so shall our enemy, death, be at last destroyed. Therefore will He be “clothed with beauty” at His resurrection, not, as now in His nativity, wrapped in swaddling clothes. Therefore He whose Heart is now brimming over with mercy, Who now judgeth no man, will then, at His rising, gird Himself, and with the cincture of justice will seem to restrain, so to speak, the flowing robes of His mercy. For from that time He shall be prepared for the judgement, which is reserved for our resurrection. And therefore He comes now as a Little One, in order to give mercy the precedence, and that mercy, going before, may temper the severity of the final judgement which must follow’.

from the first sermon for Christmas Day by St Bernard of Clairvaux, 1090-1153