Exodus 20:14 (The Six Commandment)
Thou shalt not commit adultery.
Since he returned to Plains, Georgia, from Washington after losing his re-election bid to Ronald Reagan in 1980, Carter has taught Sunday school at the local Maranatha Baptist Church. Jimmy Carter publishes study Bible, discusses faith-filled life. Carter brings some serious credentials to those notes. He served just one term as Georgia governor and one term as president, but is working on his seventh decade as a Sunday school teacher.
"Thou shalt not commit adultery." This is one of the shorter Ten Commandments and probably has the form it originally did when written, unlike the much longer commandments that were probably added to over the centuries.
The problem, naturally enough, lies with the meaning of the word "adultery". People today tend define it as any act of sexual intercourse outside of marriage or, perhaps a bit more narrowly, any act of sexual intercourse between a married person and someone who is not their spouse. That is appropriate in contemporary society but it isn’t not how the word has always been defined.
The ancient Hebrews in particular had a very restricted understanding of the concept and limited it to just sexual intercourse between a man and a woman who was either already married or at least betrothed. The marital status of the man was irrelevant. Thus, a married man was not guilty of “adultery” for having sex with an unmarried woman.
Many have argued that adultery should include lustful thoughts, lustful words, polygamy, etc. Warrant for this is justified by the words of Jesus: "You 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." (Matthew 5:27-28)
By Analysis of the Ten Commandments, Austin Cline, About.com