Please enlighten me as to what the difference is between fornication and adultery. A few of us had quite a discussion about it after our midweek services this evening.
The Greek word translated as fornication, or sexual immorality, is porneia. The Greek word translated as adultery is moicheia.
In classical Greek, porneia was used to refer to prostitution. As the word evolved, it denoted unchastity or illicit sexual relations of any kind in later writings. [Source: The Complete Biblical Library: Greek-English Dictionary].
In the Septuagint, porneia was used metaphorically to describe Israel's unfaithfulness to her husband, the Lord. In Jehu's charge, "What peace, as long as the harlotries of your mother Jezebel and her witchcraft are so many?" (II Kings 9:22), the word "harlotries" was translated as porneia in the Greek Septuagint. In Ezekiel, God speaks of "marrying" Israel, ""Yes, I swore an oath to you and entered into a covenant with you, and you became Mine," says the Lord GOD" (Ezekiel 16:8). But Israel became unfaithful and committed harlotries (porneia in the Greek) (Ezekiel 16:15, 22). In Hosea, the prophet was told to marry a prostitute. "When the LORD began to speak by Hosea, the LORD said to Hosea: "Go, take yourself a wife of harlotry and children of harlotry, for the land has committed great harlotry by departing from the LORD"" (Hosea 1:2). Once again "harlotry" in this verse is porneia in the Septuagint; thus, the sexual acts she commit before marriage were porneia. But later she continued to be unfaithful to her husband and God used this to represent His relationship with Israel. "Bring charges against your mother, bring charges; for she is not My wife, nor am I her Husband! Let her put away her harlotries from her sight, and her adulteries from between her breasts" (Hosea 2:2). Once again, "harlotries" is porneia and is made equivalent to "adulteries" in this verse.
In Theological Dictionary of the New Testament, it notes that in "Later Judaism shows us how the use of porneia, etc. gradually broadened as compared with the original usage. In the first instance porneia is mostly 'harlotry,' 'extra-marital intercourse,' ... often with adultery, ... Materially, however, it often means 'adultery,' ..."
In the New Testament, we can make this general observation: When porneia is used independently, it refers to all immoral sexual acts. When it is used in a list with moicheia (the Greek word for "adultery"), it takes on a narrower definition of immoral sexual acts before marriage, and moicheia refers to immoral sexual acts after marriage.
Walter Baurer's A Greek-English Lexicon of the New Testament and Other Early Christian Literature defines porneia as "unlawful sexual intercourse, prostitution, unchastity, fornication ... the sexual unfaithfulness of a married woman." He further notes that in Matthew 5:32 and 19:9 "The specific word for adultery does not appear in the exceptive phrase simply because a general expression occurs in Deuteronomy [24:1]."
The fact that fornication includes adultery when it is used independently is not the desire of people wishing to broaden the definition so they can have more excuses for remarriage after divorce. It is simply an acknowledgment of how the word is used in that time. As A. T. Robertson stated in Word Pictures in the New Testament, after examining many competing objections to the exception phrase in Matthew 5:32 and 19:9, "it is plain that Matthew represents Jesus in both places as allowing divorce for fornication as a general term (porneia) which is technically adultery (moicheia from moichaô or moicheuô)."
The fact that Jesus permitted an exception that allows remarriage after divorce in the case of sexual immorality does not translate into a loose view of marriage. The disciples saw Jesus' statement as being severely strict. "His disciples said to Him, "If such is the case of the man with his wife, it is better not to marry"" (Matthew 19:10). Divorce is hated because sin is being committed by one or both parties.
"And this is the second thing you do: You cover the altar of the LORD with tears, with weeping and crying; so He does not regard the offering anymore, nor receive it with goodwill from your hands. Yet you say, "For what reason?" Because the LORD has been witness between you and the wife of your youth, with whom you have dealt treacherously; yet she is your companion and your wife by covenant. But did He not make them one, having a remnant of the Spirit? And why one? He seeks godly offspring. Therefore take heed to your spirit, and let none deal treacherously with the wife of his youth. "For the LORD God of Israel says that He hates divorce, for it covers one's garment with violence," says the LORD of hosts. "Therefore take heed to your spirit, that you do not deal treacherously."" (Malachi 2:13-16).
There is a reason that Jesus used a broader term than adultery for the exception. It would include incest, bestiality, homosexuality, and other sexual sins, as well as adultery. All these sins break the terms of the marriage covenant.