Matthew 19:8-9

Moses, for the hardness of your heart. Moses "suffered" some things that were not right on account of "the hardness of your heart", a low state of morals. A people cannot be lifted from moral depravity to a high standard at once. Hence the law permitted some things that were below the perfect standard of Christ.

From the beginning. In the beginning there was no divorce and no polygamy. The first polygamist was the race of Cain (Ge 4:19).
I say unto you. We have here Christ's law of divorce in contrast with that of Moses.

Except [it be] for fornication. There is only one sufficient cause of divorce; that is, unfaithfulness to the marriage relation.

Committeth adultery. Because he is married still to his former wife, who is still his wife in spite of the divorce; so, too, if any man marries the divorced woman, he marries another man's wife.
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