Matthew 19:7-9

7Then the Pharisees said to Jesus, ‘Moses said that a man could write a letter to say that he and his wife are no longer married. Then the man can send the woman away. Why did Moses say this?’

8Jesus answered them, ‘Moses said this because you people did not want to obey God. All these things were different at the start, when God made the world.

9But now I say to you: A man must not send his wife away and marry another woman. If he does that, it is the same as if he had sex with another man's wife. A man may only send his wife away if she has had sex with another man.’