Matthew 5:27-31-27:Ye have heard that it was said by them of old time,Thou shall not commit adultery.

28:but I say unto you, that whosoever looketh on a woman to lust after her hath commited adultery with her already in his heart.
29:and if the right eye offended 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.

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.
31:it hath been said, whosoever shall put away his wife, let him give her a writing of divorcement:
32:but I say unto you, that whosoever shall put away his wife, saving for the cause of fornication, causeth her to commit adultery: and whosoever shall marry her that is divorced commiteth adultery.

So basically, if you look at a woman, you should gouge out your eye and throw it away, because you have committed adultery. And anyone that marries a woman who has been divorced is also committing adultery.