If a man is found lying with another man’s wife, both the man who slept with her and the woman must die. You must purge the evil from Israel.
Jewish Publication Society of America Version (JPS1917) - Deuteronomy 22:22 >If a man be found lying with a woman married to a husband, then they shall both of them die, the man that lay with the woman, and the woman; so shalt thou put away the evil from Israel.