John Calvin Commentary Matthew 5:27

"Ye have heard that it was said, Thou shalt not commit adultery:" — Matthew 5:27 (ASV)

Thou shalt not commit adultery. Christ proceeds with his subject and shows that the law of God not only has authority over life, in a political view, to form outward conduct, but that it also requires pure and holy affections of the heart.

We must remember what I have already stated: that although Christ quotes the very words of the law, it is the gross and false meaning that had been put upon it by dishonest interpreters that he blames. He has already told us that he did not come as a new Legislator, but as the faithful expounder of a law that had already been given. It might be objected that, through long practice, that interpretation had grown old. Christ expressly admits this, but meets it by saying that the antiquity of an error ought not to be allowed to plead in its favor.