Leviticus 20:10

20:10 And the man that committeth adultery with [another] man’s wife, [even he] that committeth adultery with his neighbour’s wife, the adulterer and the adulteress shall surely be put to death.

Matthew 5:27-30

5:27 Ye have heard that it was said by them of old time, Thou shalt not commit adultery: 5:28 But I say unto you, That whosoever looketh on a woman to lust after her hath committed adultery with her already in his heart. 5:29 And if thy right eye offend thee, pluck it out, and cast [it] from thee: for it is profitable for thee that one of thy members should perish, and not [that] thy whole body should be cast into hell. 5:30 And if thy right hand offend thee, cut it off, and cast [it] from thee: for it is profitable for thee that one of thy members should perish, and not [that] thy whole body should be cast into hell.