Matthew 19:3-8

3And the Pharisees came to him tempting him, and saying, Is it lawful for a man to put away his wife for every cause?

4But he answering said [to them], Have ye not read that he who made [them], from the beginning made them male and female,

5and said, On account of this a man shall leave father and mother, and shall be united to his wife, and the two shall be one flesh?

6so that they are no longer two, but one flesh. What therefore 1God has joined together, let not man separate.

7They say to him, Why then did Moses command to give a letter of divorce and to send [her] away?

8He says to them, Moses, in view of your hardheartedness, allowed you to put away your wives; but from the beginning it was not thus.