Charles Ellicott Commentary Matthew 19:9

"And I say unto you, Whosoever shall put away his wife, except for fornication, and shall marry another, committeth adultery: and he that marrieth her when she is put away committeth adultery." — Matthew 19:9 (ASV)

Whosoever shall put away his wife — The questions arising from this proclaimed law have been discussed in the notes on Matthew 5:32. One serious difference, however, must be noted. In the earlier form of this command, the text says a man who divorces his wife for any reason other than adultery causeth her to commit adultery. Here, the statement is more emphatic, focusing on the husband's own guilt: by contracting another marriage, he commits adultery.

The most that the law of Christ allows in such a case is a legal separation (a divorce a mensa et thoro, or “from bed and board”), not a full divorce that dissolves the marriage bond (a vinculo). Legislation that permits a complete divorce on other grounds, such as cruelty or desertion, is justified—if it can be justified at all—only on the grounds of the hardness of heart that makes such a concession necessary. It is interesting to compare this with Saint Paul’s treatment of cases not covered by the letter of this command in 1 Corinthians 7:10–15.