The Bible does not specifically directly address this issue. It’s a matter of wisdom and being mindful of temptation.
In the culture of the time in which the Bible was written, specifically in the Eastern lifestyle, most women did not live their lives alone; they either lived with family or with their husbands. The exceptions were generally widows (who either were cared for by their children or married off to members of their late husband’s family) and prostitutes who used their private dwellings to conduct their business.
In contrast, our modern society frequently has single people living on their own for some time before deciding to settle down. In this setting, many Christian couples have wondered if rooming with their significant other before marriage is a sin.
In and of itself, it’s not. However, the invitation it opens for temptation that does lead to sin must be taken very, very seriously.
This issue is often particularly pressing for Christian couples who are engaged or “very serious” in their relationship. With life heading the direction of marriage, it can seem almost a given to take that step of moving in together before signing the marriage license. It’s just a piece of paper, after all, and since you’re already so committed, why not just live under the same roof for a few weeks or months before the wedding, right?
However, this is one of the cases where wisdom must be exercised over convenience. Particularly if the couple is planning to live as if they’re already married – i.e. with no other roommates – but is also intending to abstain until marriage, the temptation can become overwhelming.
While the act of living together before marriage is not in itself biblically forbidden, it does open the door at the top of the slippery slope toward premarital sex—which the Bible is very clear about, in many places, as being against God’s will for healthy relationships.
As much as is possible, wisdom would beg for even engaged or “very seriously dating” Christian couples to seek boarding separately until they have sealed their vow before God. Although our culture takes the issue of living together before marriage very lightly, the risks involved for the abstaining couple far outweigh the benefits of “shared space.”
In order to avoid temptation and remain upright before God, the wise thing to do is to save living together, like sex itself, for after the marriage union is complete in the eyes of God and man.