Matthew 19:7-9 New King James Version (NKJV)

⁷ They said to Him, “Why then did Moses command to give a certificate of divorce, and to put her away?”

⁸ 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. ⁹ And I say to you, whoever divorces his wife, except for ^[a]sexual immorality, and marries another, commits adultery; and whoever marries her who is divorced commits adultery.”