You have heard that it was said by them of old time, You shall not commit adultery:
All Commentaries on Matthew 5:27 Go To Matthew 5
Augustine of Hippo
AD 430
The lesser righteousness, therefore, is not to commit adultery by carnal connection; but the greater righteousness of the kingdom of God is not to commit adultery in the heart. Now, the man who does not commit adultery in the heart, much more easily guards against committing adultery in actual fact. Hence He who gave the later precept confirmed the earlier; for He came not to destroy the law, but to fulfil it.