Matthew 19:4-9

And He answered and said to them, “Have you not read that He who made them at the beginning ‘made them male and female,’ and 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’? So then, they are no longer two but one flesh. Therefore what God has joined together, let not man separate.” They said to Him, “Why then did Moses command to give a certificate of divorce, and to put her away?” He said to them, “Moses, because of the hardness of your hearts, permitted you to divorce your wives, but from the beginning it was not so. And I say to you, whoever divorces his wife, except for sexual immorality, and marries another, commits adultery; and whoever marries her who is divorced commits adultery.”