Mark 10
2 Some Pharisees approached him and asked, ‘Is it lawful for a man to divorce his wife?’ They were putting him to the test. 3 He answered them, ‘What did Moses command you?’
4 They replied, ‘Moses allowed us to draw up a writ of dismissal in cases of divorce.’
5 Then Jesus said to them, 'It was because you were so hard hearted that he wrote this commandment for you.
Apparently, God didn’t change. He tolerated something which one of His prophets decreed. Jesus points to Moses commanding this as if on his own initiative. Earliest case of God abiding by ‘bound on earth, bound in heaven; loosed on earth, loosed in heaven’, perhaps?
Jesus does however, indicate quite emphatically what God intends for us to do.
Mark 10
6But from the beginning of creation he made them male and female.
7 This is why a man leaves his father and mother,
8 and the two become one flesh. They are no longer two, therefore, but one flesh.
9 So then, what God has united, human beings must not divide.’
10 Back in the house the disciples questioned him again about this,
11 and he said to them, ‘Whoever divorces his wife and marries another is guilty of adultery against her.
12 And if a woman divorces her husband and marries another she is guilty of adultery too.’