A believer’s life now belongs to God. They have been purchased by the blood of Jesus. Our lives no longer belong to us – we are now God’s children – His own special people on earth.
But you are a chosen people, a royal priesthood, a holy nation, God’s special possession, that you may declare the praises of him who called you out of darkness into his wonderful light. 1 Peter 2:9
Because we are now God’s holy people, He commands us not to marry people who do not belong to Him. As Christians, we are only allowed to marry and get married to believers.
2 Corinthians 6:14-17 says:
Do not be yoked together with unbelievers. For what do righteousness and wickedness have in common? Or what fellowship can light have with darkness? What harmony is there between Christ and Belial? Or what does a believer have in common with an unbeliever? What agreement is there between the temple of God and idols? For we are the temple of the living God. As God has said: “I will live with them and walk among them, and I will be their God, and they will be my people.” Therefore, “Come out from them and be separate, says the Lord. Touch no unclean thing, and I will receive you.”
Because we are now God’s children, the Holy Spirit of God now lives in us, He has made us a dwelling and temple of God.
The believer now lives to please God and not their own flesh. When we love and marry someone who is not a Christian, that person can now influence you. Their values and God’s values are different; and because of that they can affect your love and service to God. They also have authority and influence over your children and can easily destroy the Godly influence you are placing upon your children.
In addition, a non-believer is not under God’s influence and protection. So they can easily bring the influence of demonic forces into your home and family.
Because of that God commands His people only to marry someone who shares their faith. When we do that, we receive a blessing from the Lord and save ourselves from a lot of pain and trouble that comes from disobeying this command.
This instruction is applicable only to those who are not married: the single, the single mothers & fathers; and the widows and widowers who want to get married.
For those who are already married to an unbeliever, you must not divorce your unbelieving husband or wife.
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. [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 Corinthians 7:12,13,16
So the believer who has an unbelieving spouse must pray for them to be saved. Invite them to church, preach the gospel to them and above everything – live a godly life so that they may see your faith in action and believe in Jesus.