Luke 2:7

He finds man in his corrupt affections become like the beasts that perish, and therefore He is laid in the manger, in the place of food, that we changing the life of beasts, might be brought to the knowledge that befits man, partaking not of hay, but of the heavenly bread, the lifegiving body.

(Diem Nat. Christi.) Though coming in the form of man, yet not in every thing is He subject to the laws of man's nature; for while His being born of a woman, tells of human nature; virginity becoming capable of childbirth betokens something above man. Of Him then His mother's burden was light, the birth immaculate, the delivery without pain, the nativity without defilement, neither beginning from wanton desire, nor brought to pass with sorrow. For as she who by her guilt engrafted death into our nature, was condemned to bring forth in trouble, it was meet that she who brought life into the world should accomplish her delivery with joy. But through a virgin's purity He makes His passage into mortal life at a time in which the darkness was beginning to fail, and the vast expanse of night to fade away before the exceeding brightness of the light. For the death of sin had brought an end of wickedness which from henceforth tends to nothing by reason of the presence of the true light which has illuminated the whole world with the rays of the Gospel.

St. Luke has briefly explained the manner, time, and also the place in which Christ was born in the flesh; the manner, that is, in which the espoused has conceived, a virgin has born offspring. On thy account then am I weak, in Himself is He strong. On thy account am I poor, in Himself is He rich. Consider not what thou seest, but acknowledge that thou art redeemed. I owe more, O Lord Jesus, to Thy sufferings that I am redeemed, than to Thy works that I am created. It were no advantage to be born, had it not advantaged me to be redeemed also.

(non occ.) Surely if He had so willed it, He might have come moving the heavens, making the earth to shake, and shooting forth His thunderbolts; but such was not the way of His going forth; His desire was not to destroy, but to save; and to trample upon human pride from its very birth, therefore He is not only man, but a poor man, and has chosen a poor mother, who had not even a cradle where she might lay her new born Child; as it follows, and she laid him in the manger.

(cont. Helvid.) From this Helvidius strives to prove that no one can be called firstborn who has not brothers, as he is called only-begotten who is the only son of his parents. But we thus determine the matter. Every only-begotten is firstborn, not every firstborn is only-begotten. We say not that he is first-begotten whom others follow, but before whom there is no one; (otherwise, supposing there is no firstborn but who has brothers following him, there are then no firstlings due to the priests as long as there are no others begotten;) lest perchance when no birth follows afterward, there should be an only-begotten and not a firstborn. Now here was no midwife, no tender anxiety of women; she wrapped the Child up in swaddling clothes, herself both mother and midwife.