36 If anyone is worried that he might not be acting honorably toward the virgin he is engaged to, and if his passions are too strong and he feels he ought to marry, he should do as he wants. He is not sinning. They should get married.37 But the man who has settled the matter in his own mind, who is under no compulsion but has control over his own will, and who has made up his mind not to marry the virgin—this man also does the right thing. 38 So then, he who marries the virgin does right, but he who does not marry her does better. 39 A woman is bound to her husband as long as he lives. But if her husband dies, she is free to marry anyone she wishes, but he must belong to the Lord.40 In my judgment, she is happier if she stays as she is—and I think that I too have the Spirit of God.—1 Cor. 7:36-40 NIV
This is Paul’s warning against sex outside of marriage. In those times, most marriages were pre-arranged, so the person knew who they would be marrying. Therefore, Paul could make this warning specific to a particular person. In today’s world of dating, the warning would have to be generalized to mean any person with whom you are in any sort of social relationship. The couple, if they are unable to control themselves physically, should either stop the relationship or agree to get married and do so before the physical relationship leads both of them to sin. Either decision will keep us from doing the wrong thing. That does not mean that we rush into marriage just so we can have sex. There are “good” things and then there are “God” things. Search for and do the “God” thing, not the thing that feels good. Experience teaches us that if our marriage choices are not soaked in prayer, the end result can be disastrous. Once the marriage is consummated, praying together will keep the marriage together. Less than 1% of marriages where the couple pray together daily end in divorce.
If you make the decision to marry, then you are bound to each other “until death do us part”. Jesus set the example for us since He will never forsake the church
31 “For this reason a man will leave his father and mother and be united to his wife, and the two will become one flesh.” 32 This is a profound mystery—but I am talking about Christ and the church. 33 However, each one of you also must love his wife as he loves himself, and the wife must respect her husband.—Eph. 5:31-33 NIV
12 To the rest I say this (I, not the Lord): If any brother has a wife who is not a believer and she is willing to live with him, he must not divorce her. 13 And if a woman has a husband who is not a believer and he is willing to live with her, she must not divorce him. 14 For the unbelieving husband has been sanctified through his wife, and the unbelieving wife has been sanctified through her believing husband. Otherwise your children would be unclean, but as it is, they are holy. 15 But if the unbeliever leaves, let it be so. The brother or the sister is not bound in such circumstances; God has called us to live in peace. 16 How do you know, wife, whether you will save your husband? Or, how do you know, husband, whether you will save your wife?—1 Cor. 7:12-16 NIV
If a Christian should decide to marry a non-Christian, the Christian is bound to those vows and must remain faithful to the non-believer. The unbeliever may choose to leave, in which case, the believer should allow them to go. Certainly it would have been better if the Christian had followed the advice to “not be unequally yoked” .
14 Do not be yoked together with unbelievers. For what do righteousness and wickedness have in common? Or what fellowship can light have with darkness?– 2 Cor. 6:14 NIV
The believer can grant the divorce to the unbeliever and is no longer bound to that person. We should let them go in peace. Are we then free to marry someone else? That is a question that you need to address to the Holy Spirit and follow His leadership.
12 Therefore, my beloved, as you have always obeyed, not as in my presence only, but now much more in my absence, work out your own salvation with fear and trembling; 13 for it is God who works in you both to will and to do for His good pleasure.–Phil. 2:12,13 NKJV
8 Now to the unmarried and the widows I say: It is good for them to stay unmarried, as I do. 9 But if they cannot control themselves, they should marry,for it is better to marry than to burn with passion. 10 To the married I give this command (not I, but the Lord): A wife must not separate from her husband. 11 But if she does, she must remain unmarried or else be reconciled to her husband. And a husband must not divorce his wife..—1 Cor. 7:8-11 NIV
Paul feels that his not being married gives him more freedom and more time to serve the Lord. He says that it would be good if you would stay unmarried unless this would cause you to commit the sin of sex outside of marriage. If you desire intimate companionship and children, then you should marry a Godly person. But once you make that commitment, you must remain faithful to that one spouse. God would prefer that we not divorce at all, but He gave us free wills and He knew that we would do that. Paul is writing a short paraphrase of what Jesus told the Pharisees in Matthew 19.
7 “Why then,” they asked, “did Moses command that a man give his wife a certificate of divorce and send her away?”
8 Jesus replied, “Moses permitted you to divorce your wives because your hearts were hard. But it was not this way from the beginning. 9 I tell you that anyone who divorces his wife, except for sexual immorality, and marries another woman commits adultery.”—Matt 19:7-9 NIV
Notice that when Jesus answers, He replaces the word “commanded” with the word “permitted”. Because of our free wills, God will not force anyone to stay married, but He would prefer that we allow Him to show us how to forgive and forget.