Augustine of Hippo
Catena Aurea · Johannesevangelium 1
The next day John seeth Jesus coming to him, and saith, Behold the Lamb of God, which taketh away the sin of the world. This is he of whom I said, After me cometh a man which is preferred before me: for he was before me. And I knew him not: but that he should be made manifest to Israel, therefore am I come baptizing with water.
(Tr. iv. c. 10) If the Lamb of God is innocent, and John is the lamb, must he not be innocent? But all men come of that stock of which David sings sorrowing, Behold, I was conceived in wickedness. (Ps. 51:5) He then alone was the Lamb, who was not thus conceived; for He was not conceived in wickedness, nor in sin did His mother bear Him in her womb, Whom a virgin conceived, a virgin brought forth, because that in faith she conceived, and in faith received.