A: No; Matthew makes explicit what the audiences of Mark and Luke would consider implicit. Under the Law of Moses, a wife found guilty of adultery would be executed; this law was apparently adapted, after the Roman colonization of the Hasmonean kingdom (by Pompey in 63 B.C.) and Roman laws became the law of the land. The Romans denied the local authorities the right to enforce the death penalty in such cases (though theoretically an adulterous wife could be lynched) so instead of actually executing the guilty wife, she was declared legally dead in the eyes of her family. The husband was then free to remarry as if his wife had died.
Thats the scenario that I think is lurking in the background here. Unfortunately theres not much extra-Biblical evidence for this; its a guess at what the rabbis of that era did when they regarded a woman to be guilty of adultery but their governing elders were, under Rome, prohibited from executing her. But such an adaptation is not unlike other adaptations that were made when law-enforcement had to be adapted in light of extenuating circumstances. Also, this has the advantage of interlocking well with what Paul says in First Cor. 7:10-17.
The meaning of Matthew 19:9 would thus be that (a) a man is forbidden to divorce his wife unless she has been sexally unfaithful to him, (b) if he divorces her for some other reason, and remarries, when he consummates the union with the second woman he marries, he will be committing adultery, and (c) if a man divorces his wife with just cause -- i.e., because she committed adultery -- then if another man marries the divorced woman, he is committing adultery.
Another solution -- though to me its severity raises a fresh problem -- is pointed out in an essay provided earlier by OriginalMissJesus (see the responses at Matthew 5:31): the term rendered sexual immorality or fornication in Matthew 19:9 is understood to mean not fornication but incest, meaning that the man and woman are found to be too closely related and their marriage may lawfully be annulled on the grounds that it was never legal to begin with. On this premise, one would harmonize Jesus statements with Pauls statements either by approaching Jesus statements as something that was literally applicable only during the covenant of the Law, or by approaching some of Pauls statements as non-authorative but exemplary self-quotes.
This, btw, is part of a larger issue -- divorce and remarriage in the covenant of grace -- which Dr. Craig Keehner of Duke University has explored in detail in the book And Marries Another. Even if one does not agree with all of his conclusions, his copiously footnoted book on this subject is well worth digesting.
Yours in Christ,
Waterrock
