1 Cor 7:
10To the married I give this charge (not I, but the Lord): the wife should not separate from her husband
11(but if she does, she should remain unmarried or else be reconciled to her husband), and the husband should not divorce his wife.
12To the rest I say (I, not the Lord) that if any brother has a wife who is an unbeliever, and she consents to live with him, he should not divorce her.
13If any woman has a husband who is an unbeliever, and he consents to live with her, she should not divorce him.
14For the unbelieving husband is made holy because of his wife, and the unbelieving wife is made holy because of her husband. Otherwise your children would be unclean, but as it is, they are holy.
15But if the unbelieving partner separates, let it be so. In such cases the brother or sister is not enslaved. God has called you
b to peace.
16For how do you know, wife, whether you will save your husband? Or how do you know, husband, whether you will save your wife?
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Matthew 5:
31 “It was also said, ‘Whoever divorces his wife, let him give her a certificate of divorce.’ 32 But I say to you that everyone who divorces his wife, except on the ground of sexual immorality, makes her commit adultery, and whoever marries a divorced woman commits adultery.
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Matthew 19 - in context, says the same thing as Matthew 5:
7 They said to him, “Why then did Moses command one to give a certificate of divorce and to send her away?” 8 He said to them, “Because of your hardness of heart Moses allowed 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 sexual immorality, and marries another, commits adultery.”