Jesus and Divorce Law

Jesus raised the standard on granting divorce from the standard that was given under Old Covenant Law. Under the Old Covenant that applied to national Israel a man could divorce his wife by giving her a certificate of divorce and sending her away.
Deut. 24:1 “When a man takes a wife and marries her, if then she finds no favor in his eyes because he has found some indecency in her, and he writes her a certificate of divorce and puts it in her hand and sends her out of his house, and she departs out of his house,
Jesus in the Sermon on the Mount gave a new and higher standard.
Mt. 5:31-32 “It was also said, ‘Whoever divorces his wife, let him give her a certificate of divorce.’ 32 But I say to you that everyone who divorces his wife, except on the ground of sexual immorality, makes her commit adultery, and whoever marries a divorced woman commits adultery.
This is one of several statements by Jesus where he changes Old Covenant law with the phrase, “But I say to you”. Some doctrinal interpretations hold that Jesus was simply correcting the misapplication of the law by the religious leaders. However, in this case and also with adultery and murder Jesus quotes exactly what the law and the Ten Commandments stated in the Old Testament. Therefore, Jesus is not just correcting a wrong interpretation; he is raising the requirements for divorce to a higher standard with the “But I say to you” statements. He is giving the Christian standard for true believers, whereas the Old Covenant was given to an entire nation most of whom were unredeemed. Jesus explained this more fully when he said:
Mt. 19:3-9 And Pharisees came up to him and tested him by asking, “Is it lawful to divorce one's wife for any cause?” 4 He answered, “Have you not read that he who created them from the beginning made them male and female, 5 and said, ‘Therefore a man shall leave his father and his mother and hold fast to his wife, and the two shall become one flesh’? 6 So they are no longer two but one flesh. What therefore God has joined together, let not man separate.” 7 They said to him, “Why then did Moses command one to give a certificate of divorce and to send her away?” 8 He said to them, “Because of your hardness of heart Moses allowed you to divorce your wives, but from the beginning it was not so. 9 And I say to you: whoever divorces his wife, except for sexual immorality, and marries another, commits adultery.”
Jesus says what both the Old Testament and the New Testament says in many places and that is Israel was not a spiritually redeemed people. When Jesus told the Pharisees that the law allowed divorce because of their hardness of heart, he was verifying they were NOT spiritually redeemed. Contrast this statement with the beatitudes where Jesus describes the characteristics of spiritually redeemed Christians. The Old Covenant even allowed polygamy [Deut. 21:15]. If Jesus had not raised these standards, Christian marriage and the details concerning adultery in the New Covenant would be very different. The Old Testament pointed to the new standards that Jesus would implement and told us to listen to him, just as God the Father said at the Mt. of Transfiguration.
Deut. 18:15 “The LORD your God will raise up for you a prophet like me from among you, from your brothers—it is to him you shall listen—