Deuteronomy 24:4

The woman was held to be defiled by her second marriage, and thus by implication, the marrying of a woman who had been divorced was pronounced immoral, as is by our Lord explicitly asserted ( Matthew 5:32 ). The prohibition of a return of the wife to her first husband, as well as the necessity of a formal bill of divorcement being given to the woman before she could be sent away, could not fail to be checks on the license of divorce, as doubtless they were intended to be.