3 Jesus answered them with a question: "What did Moses say in the law about divorce?" 4 "Well, he permitted it," they replied. "He said a man can give his wife a written notice of divorce and send her away." 5 But Jesus responded, "He wrote this commandment only as a concession to your hard hearts.
Matthew Henry's Commentary on Mark 10:3-5
Commentary on Mark 10:1-12
(Read Mark 10:1-12)
Wherever Jesus was, the people flocked after him in crowds, and he taught them. Preaching was Christ's constant practice. He here shows that the reason why Moses' law allowed divorce, was such that they ought not to use the permission; it was only for the hardness of their hearts. God himself joined man and wife together; he has fitted them to be comforts and helps for each other. The bond which God has tied, is not to be lightly untied. Let those who are for putting away their wives consider what would become of themselves, if God should deal with them in like manner.