Matthew 19:3-9

³And Pharisees came up to him and tested him by asking, "Is it lawful to divorce one's wife for any cause?" ⁴He answered, "Have you not read that he who made them from the beginning made them male and female, ⁵and said, `For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one flesh'? ⁶So they are no longer two but one flesh. What therefore God has joined together, let not man put asunder." ⁷They said to him, "Why then did Moses command one to give a certificate of divorce, and to put her away?" ⁸He said to them, "For your hardness of heart Moses allowed you to divorce your wives, but from the beginning it was not so. ⁹And I say to you: whoever divorces his wife, except for unchastity, and marries another, commits adultery."