Theophilus of Antioch

And the voice of the Gospel teaches still more urgently concerning chastity, saying: "Whosoever looks on a woman who is not his own wife, to lust after her, has committed adultery with her already in his heart." [Matthew 5:28] "And he that marries," says [the Gospel], "her that is divorced from her husband, commits adultery; and whosoever puts away his wife, saving for the cause of fornication, causes her to commit adultery." [Matthew 5:32] Because Solomon says: "Can a man take fire in his bosom, and his clothes not be burned? Or can one walk upon hot coals, and his feet not be burned? So he that goes in to a married woman shall not be innocent." [Proverbs 6:27-29]