If I had not come and spoken unto them, they had not had sin. — In this and the following verses (John 15:22-25) our Lord shows the sinfulness of the world’s hatred, because it was in the face of His revelation to them by both word (John 15:22) and work (John 15:24). Apart from this revelation, their sin would have belonged to the times of ignorance, which God overlooked (Acts 17:30-31). It would have been the negative evil of men who know not. It was now the positive evil of men who, knowing the truth, wilfully reject it.
But now they have no cloke for their sin. — Better, as in the margin, they have no excuse for their sin. The Greek phrase occurs only here in the New Testament. The word “cloke” as used with sin is familiar to us from the exhortation in the Book of Common Prayer. The idea is rather to cover up, to hide as with a garment, so that they may not be seen; whereas here the idea is of excuse for manifest sin.