Theophylact of Ohrid
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.
(in loc.) Why does he say the sin of the world, not sins? Because he wished to express sin universally: just as we say commonly, that man was cast out of paradise; meaning the whole human race.