"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."
— 1 Corinthians 7:39
Quick Answer
Yes, Scripture instructs believers to marry only “in the Lord” (1 Corinthians 7:39) and warns against being “yoked together with unbelievers” (2 Corinthians 6:14), so knowingly choosing to marry a nonbeliever disregards God's guidance. This is different from an existing marriage to a nonbeliever, which Scripture calls believers to remain faithful in, not abandon (1 Corinthians 7:12-13).
A Direct Question Deserves a Direct Answer
This question usually comes from someone already emotionally invested, dating a kind, wonderful person who simply does not share their faith, hoping for permission rather than principle. It deserves an honest answer rather than either harsh condemnation or convenient dismissal: Scripture instructs believers to marry in the Lord (1 Corinthians 7:39), and choosing to knowingly marry a nonbeliever runs against that clear instruction.
Calling this sin is not the same as saying every interfaith marriage is a disaster, or that a nonbelieving spouse cannot become a wonderful husband or wife, or even later come to faith. It simply means the choice to enter such a marriage, made with eyes open, disregards guidance God gave for a believer's good.
What Scripture Actually Says
Paul's instruction to widows considering remarriage is direct: they are free to marry whomever they wish, but he must belong to the Lord (1 Corinthians 7:39). Earlier, he warns believers broadly not to be yoked together with unbelievers, asking what partnership light can have with darkness, or a believer with an unbeliever (2 Corinthians 6:14-15). The consistent instruction is marriage between two believers.
This is not merely Paul's personal preference; it reflects the same principle God gave Israel through Moses, warning that intermarriage with those devoted to other gods would turn hearts away from following the Lord (Deuteronomy 7:4), and it is illustrated tragically in Solomon's own life, where foreign wives who did not share his devotion eventually turned his heart away from the Lord (1 Kings 11:3-4).
Why This Isn't Arbitrary
God does not restrict this out of harshness but out of realism about how marriage actually shapes a person over decades. Marriage draws two people's entire lives into shared decisions, how to raise children, how to spend money, how to spend Sundays, what to believe about eternity itself. A spouse who does not share your faith cannot fully share your deepest priorities, and the pull, over years, tends to move the believing spouse away from wholehearted devotion rather than the nonbelieving spouse toward it.
This is a sober warning grounded in real spiritual danger, not an arbitrary religious rule. God's instructions about marriage are consistently for His people's flourishing, even when they cut against strong feelings in the moment.
Consider how many decisions a married couple must make together over a lifetime that depend directly on shared faith: how to pray through a crisis, whether to give generously, how to respond when a child asks hard questions about God, what hope to lean on at a funeral. A spouse who does not share your faith is not merely a different personality to accommodate, but a partner who cannot fully walk beside you through the very moments marriage is built to weather together.
If You're Already Married to a Nonbeliever
If you are reading this already married to a nonbeliever, whether you married before coming to faith, or your spouse's faith later changed, please hear this clearly: Scripture does not call you to leave. If a believer has a spouse who is not a believer and that spouse is willing to live with them, they must not seek divorce (1 Corinthians 7:12-13). Your marriage remains a real, honorable marriage, and your presence in it is described as a sanctifying influence in your household (1 Corinthians 7:14).
Live out your faith consistently, pray faithfully for your spouse, and trust God with what you cannot control, remembering Paul's own hopeful question: how do you know whether you will save your husband or wife (1 Corinthians 7:16). Conviction about the wisdom of marrying a believer going forward is not condemnation of a marriage already made.
If You're Considering It Now
If you are not yet married and weighing this decision, take the warning seriously precisely because it comes from love, not legalism. Talk honestly with mature believers, examine your own heart for rationalization, and consider the weight of raising children, worshiping, and facing life's hardest moments with someone who does not share your ultimate hope.
This is not a small matter to decide on feeling alone. Pray earnestly, seek godly counsel, and trust that obedience here, even when costly in the moment, is never obedience wasted, because the God who gave this instruction is the same God who cares deeply about your joy, not merely your compliance.
It also helps to remember that this teaching is never meant to make a nonbelieving person seem unworthy of love or friendship. Christians are called to genuinely love and befriend people who do not share their faith. The question here is specifically about the unique, lifelong, one-flesh covenant of marriage, not about the worth of the person you may currently be considering marrying.