By Luke Lancaster
Jesus says in Matthew 19:9 that "Whoever divorces his wife, except for unchastity, and marries another, commits adultery" (see also Matt. 5:32). Many non-Catholics groups will attempt to say that Jesus here allows for remarriage if the spouse commits "unchastity." This exception clause in Matthew’s Gospel can be looked at in three different ways.
First, because the Greek word, porneia, has a wide semantic range, it could be interpreted as adultery, to which the Fathers of the Church said that if a spouse committed adultery, then the couple could separate, but they could not remarry. They maintained that, when Jesus said, "except for unchastity," He was referring to divorce (the word previously said), and not to remarriage. For Jesus speaks about the topic remarriage after talking about divorce and unchastity.
St. Augustine explains the issue as referring to the ability of spouses to separate and divorce civilly if there was the issue of adultery. But the couple cannot remarry. For the apostles say in the next verse (Matt. 19:10) that it would be better to not marry, indicating that the apostles understood Jesus to be saying that remarriage is impossible.
Another interpretation is that the exception clause refers to a marriage never being contracted or valid at all because the couple had a close blood relation. That idea is found in Acts 15:20, 29 (background: Lev. 18:6-18) and 1 Cor. 5:1-2.
The final interpretation is that the exception clause was saying that divorce and remarriage was adultery regardless of what the Old Testament has to say about the matter. So, "except for unchastity" would mean "regardless of the OT grounds for divorce" (Hahn and Mitch, Ignatius Catholic Study Bible, p. 41).
We should keep in mind the fact that this phrase "except for unchastity," is only found in Matthew's Gospel. Mark's Gospel does not include it (Mk. 10:11, 12) and Luke's Gospel does not include it (Lk. 16:18). St. Paul does not have it either, saying that separated partners should be reconciled or remain single (1 Cor. 7:10-11). Nothing about remarriage. So, Matthew's Gospel should not be interpreted as allowing for remarriage if a spouse is unchaste. For then, if I wanted to get out of a marriage, all I would have to do is be unchaste! And everybody struggles with chastity, so everybody could remarry! So, as we can see, this is not the best interpretation of Christ's words.