Note 19 at Mt. 5:32: Just as with murder (vv. 21-22) and adultery (vv. 27-28), Jesus is taking divorce one step further than the Mosaic law did. Under Moses' law, the people were allowed to get a divorce for any reason (Mt. 19:3; Mk. 10:2-4), much as we see today. Divorce was permitted under the Old Testament (as was polygamy) because of the hardness of people's hearts, but Jesus revealed that this was not God's original plan (Mk. 10:5-9). Jesus permits divorce under the New Testament for the sole reason of fornication simply because the fornicator has already broken the union.