Matthew 19:7-9

7They say to him, Why did Moses then command to give a writing of divorcement, and to put her away? 8He saith to them, Moses because of the hardness of your hearts permitted you to put away your wives: but from the beginning it was not so. 9And I say to you, Whoever shall put away his wife, except for immorality, and shall marry another, committeth adultery: and whoever marrieth her who is put away committeth adultery.