Take a close look at Matthew 19 and I believe it is clear that “porneia” refers to unlawful marriages which were classified as incest.
The Sadducees believed that one could divorce and remarry for any reason.
The Pharisees believe one could divorce and remarry only for limited reasons like adultery. The Pharisees asked Jesus this question:
Matt 19:3-9: “And Pharisees came up to him and tested him by asking, ‘Is it lawful to divorce one’s wife for any cause?’
He answered, ‘Have you not read that he who made them from the beginning made them male and female, and said, ‘For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one’? So they are no longer two but one. What therefore God has joined together, let not man put asunder’.
Jesus is saying that He is re-instating marriage as it was from the beginning
They said to him, ‘Why then did Moses command one to give a certificate of divorce, and to put her away?’ He said to them, “For your hardness of heart Moses allowed you to divorce your wives, but from the beginning it was not so. And I say to you, whoever divorces his wife, except for unchastity, and marries another commits adultery.”
In the time of Jesus, Jews and pagans had illegal “marriages” which were forbidden in Leviticus 18:6-23 and Leviticus 20: 10-21 which lists all sorts of unlawful practices. The unlawful marriages were considered to be incest and were referred to by the Greek word ‘porneia’ which is translated in English as fornication or unchastity.
The New Testaments was written in Greek. What we have is an English translation.
In Acts 15: 29 the pagans that converted to Christianity were told this:
“abstain from what has been sacrificed to idols and from blood and from what is strangled and from unchasitity. (porneia)
Sacrificing to idols and eating animals with blood still in them was forbidden in Leviticus 17 and fornication ( porneia) was forbidden in Leviticus 18 and 20.
In Greek this is what Jesus said:
Matt 19: 9 “And I say to you whoever divorces his wife, except for porneia, and marries another commits adultery.”
This is what Jesus is referring to in the Gospel of Matthew. He was referring to unlawful marriages. The Gospel of Matthew was written for a Jewish audience and that is why it is the only gospel to have the so-called exception clause.
Matthew 14:1-4 tells us about Herod who was living in porneia. John the Baptist was beheaded because he told Herod “It is not lawful for you to have her.” Herod was “married” to his niece who had been his brother’s wife ( and also his niece) which was porneia and therefore an unlawful marriage.
Paul uses the word porneia here for an illegal “marriage”.
1 Cor. 5:1 “It is actually reported that there is immorality (porneia) among you, and of a kind that is not found even among pagans; for a man is living with his father’s wife”
Most likely this man was living with his mother. This is why Paul says “of a kind that is not found even among pagans” and later Paul says in verse 5 “ you are to deliver this man to Satan for the destruction of the flesh that his spirit may be saved in the day of the Lord.”
Another reason we know there is not an exception clause is because it is not mentioned anywhere else.
Jesus gives no exception clause in Mark 10:11–12: “Whoever divorces his wife and marries another, commits adultery against her; and if she divorces her husband and marries another, she commits adultery.”
Luke 16:18 “Everyone who divorces his wife and marries another commits adultery and he who marries a woman divorced from her husband commits adultery.”
Paul tells us this:
1 Cor. 7:10, “To the married I give charge, not I but the Lord that the wife should not separate from her husband, but if she does, let her remain single or else be reconciled from her husband, and that the husband should not divorce his wife.”
Romans 7: 2-3, “A wife is bound to her husband as long as he lives. If her husband dies she is discharged from the law. Accordingly, she shall be called an adulteress if she lives with another man while her husband is alive.”
Going back to Matt 19: 9 “And I say to you whoever divorces his wife, except for porneia, commits adultery”
This could be translated like this. “And I say to you, whoever divorces his wife and marries another, commits adultery. Those who are living together are committing the sin of fornication but are not in a true marriage and if they marry it will not be adultery since they were never married in the first place.”
It’s clear that the apostles did not take Jesus words to mean there was an exception clause because immediately following His words they said “If such is the case of a man with his wife it is better not to marry.”
