Next, Jesus taught the law of chastity and a related law of divorce pertaining to covenant marriages. On divorce, He comments that it was written in the Law of Moses that if a man were going to put his wife away, he needed only to give her a written bill of divorcement. This is found in Deuteronomy 24:1. But instead, Jesus now said that divorce is only permissible in the case of fornication. He did not allow the same kind of latitude as was available under Deuteronomy. There were many Jewish interpretations of Deuteronomy 24, such as those that said that, if a man found any uncleanness, or anything that was undesirable about his wife, he could give her a bill of divorcement. For those people, marriage had become a simple contract between a man and a woman, and that contract could be broken unilaterally, usually by the man.
But Jesus taught that covenant marriage (see Malachi 2:14) was not that kind of bilateral relationship. Spouses bound by covenant with God, however, were only to enter into divorce under very certain conditions, probably only if they could prove that there had been a real violation of the marriage covenant. Especially in Matthew 19, Jesus explains (in answer to the question about why he disagrees with Deuteronomy 24) that what God has put together, man shall not put asunder. Jesus teaches here that covenant marriages, which involve God in the relationship, are not easy to live (Matthew 19:11). Such marriages are not unilaterally created, and thus they are not to be unilaterally terminated. There may or may not have been a way in early Christianity for some kind of an ecclesiastical determination that such a marriage could legitimately end, but such was not something that either the husband or wife should decide on their own accord without thinking about God and His will. For Jesus, the covenant relationship of marriage was sacred. In my view, what Jesus said about divorce (both in Matthew and at the temple in Bountiful) assumes a covenant relationship between the husband and wife that had been ratified, blessed, or sealed by God, and thus could not be lightly abandoned. Jesus taught that, in this new temple context, the responsibilities of marriage, divorce, and chastity will be taken much more seriously, and that the heavenly blessings, accordingly, are much higher.