The Seventh Commandment (7 of 10, God's Law) Thou shalt not commit adultery. (Exodus 20:14)

The Westminster Larger Catechism (1648),

Question 138: What are the duties required in the seventh commandment?
Answer: See http://www.swrb.com/newslett/actualNLs/WLC.htm

Question 139: What are the sins forbidden in the seventh commandment?
Answer: The sins forbidden in the seventh commandment, besides the neglect of the duties required, are, adultery, fornication, rape, incest, sodomy, and all unnatural lusts; all unclean imaginations, thoughts, purposes, and affections;all corrupt or filthy communications, or listening thereunto; wanton looks, impudent or light behavior, immodest apparel; prohibiting of lawful, and dispensing with unlawful marriages; allowing, tolerating, keeping of stews, and resorting to them; entangling vows of single life, undue delay of marriage; having more wives or husbands than one at the same time; unjust divorce, or desertion; idleness, gluttony, drunkenness, unchaste company; lascivious songs, books, pictures, dancings, stage plays; and all other provocations to, or acts of uncleanness, either in ourselves or others.

And remember the Lord Jesus Christ said:

Ye have heard that it was said by them of old time, Thou shalt not commit adultery: But I say unto you, That whosoever looketh on a woman to lust after her hath committed adultery with her already in his heart (Matt. 5:27-28).

And: 'If ye love me, keep my commandments.' (John 14:15)

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