Matthew 19:9 Does Not Restrict Divorce To Adultery

Well before Matthew 19, and afterward in Paul's writing to the Corinthians, the Bible gives specific categories of behavior that justify divorce, and they go far beyond adultery.  In Matthew 19, Jesus makes the famous but misunderstood statement that anyone who divorces their spouse and remarries commits adultery unless their former spouse practiced sexual immorality.  In contrast with the Pharisaical distortion of explicit allowance for divorce in Mosaic Law (Exodus 21:9-11, but see also Deuteronomy 24:1-4), Jesus said that divorce is not morally valid in just any circumstance as soon as it is preferred.

Exodus 21:9-11 specifies that neglect and abuse are grounds for divorce, and although the case law mentions a woman divorcing a man, the irrelevance of gender to moral obligation necessitates that this also would apply to the inverse.  1 Corinthians 7 sees Paul acknowledge that abandonment is grounds for divorce.  No one is obligated to remain in a marital covenant with someone who has broken it by leaving their spouse behind.  With neglect and abuse alone, this is already far more than adultery or broader sexual immorality that permits a severance of marriage.

Within Matthew 19:9 itself, though, Jesus does not actually say that only sexual immorality, confused by some to mean strictly adultery when all sexual sins like rape (Deuteronomy 22:25-27) would by necessity be included, legitimizes divorce.  He says that anyone who divorces their spouse except for sexual immorality and marries a new partner commits adultery.  The focus is on sexual basis for divorce and the sin of remarrying after an illicit divorce.  What Jesus states is that someone commits adultery if they do this and contrasts it with a misconception of Mosaic Law.

Deuteronomy 24:1-4 does permit divorce, and Mosaic Law is Biblically identified as the just commands (Deuteronomy 4:5-8) of a deity who never changes (Malachi 3:6), one whom Jesus affirmed (Matthew 5:17-20).  If Matthew 19 did contradict any of this, the other verses could be true because they are consistent with logical axioms and each other, but Matthew 19:9 would be false.  It would be appealing to prerequisite things it then contradicts.  However, Deuteronomy 24 does not say that divorce is mandatory or permissible in all circumstances.  It specifies that indecency, as in sin, justifies divorce.

Divorcing on emotionalistic, selfish, hypocritical, or any other kind of irrational or morally invalid grounds (the one initiating the divorce being in the wrong here) is not ending a marriage over the other party's indecency.  It is divorce for stupidity on the initiator's part.  This is what the context reveals Jesus is pushing back against; divorce is just, freeing, and healing in the right scenarios, from emotional abuse to food deprivation (see Exodus 21:9-11 again) to abandonment to true sexual indecency.  To divorce casually for irrationalistic reasons and remarry is adulterous because the prior spouse was betrayed.