When I was in college and a brand new believer, I was asked a question that caught me off guard: Where in the Bible does it say that Christians should wait until marriage to have sex?
It stumped me because a) I didn’t know my Bible at all, and b) even as an unbeliever I had taken for granted that Christians did not sleep together before marriage. I had never thought anyone would challenge that assumption. I was wrong.
In his letter to the Thessalonian Christians Paul reveals God’s will on the issue of sex before marriage to “you in the Lord” I.e. Christians. It is important to realize that this is not limited to a particular culture of time period, because Paul says this is what he received from God who inspired the writing of Scripture (as in 2 Tim 3:16-17 explains), on “how you aought to walk and to please God (1 Thess 4:1)”
If you don’t live this way you are living like the people “who do not know God” (vs 5) i.e. unbelievers. So, if a person lives this way, he should not call himself a Christian.
Here’s the passage…
1 Thessalonians 4:1 Finally, then, brothers, we ask and urge you in the Lord Jesus, that as you received from us how you ought to walk and to please God, just as you are doing, that you do so more and more. 2 For you know what instructions we gave you through the Lord Jesus. 3 For this is the will of God, your sanctification: that you abstain from sexual immorality; 4 that each one of you know how to control his own body in holiness and honor, 5 not in the passion of lust like the Gentiles who do not know God; 6 that no one transgress and wrong his brother in this matter, because the Lord is an avenger in all these things, as we told you beforehand and solemnly warned you. 7 For God has not called us for impurity, but in holiness.
To the Corinthians Paul lists the people who will not inherit the kingdom of God, i.e. those who go to hell. On his list are “sexually immoral” or “fornicators” which is a word meaning people who have sex before marriage! (1 Cor 6:9). This applies to anyone in any era and any culture who engage in sexual activity outside of the marriage covenant. Also 1 Cor 5:8 is a pithy injunction to abstain from all sexual immorality.
The writer to the Hebrews (who believed that sex was only for marriage, so these are not promiscuous pagans he is writing to, but legalistic Jewish converts), he reminds them that sex is limited to marriage:
Heb 13:4 Let marriage be held in honor among all, and let the marriage bed be undefiled, for God will judge the sexually immoral and adulterous.
And then of course there is Jesus’ teaching to the Jews was that having sexual desire in your heart (lust) for a woman who is not your wife, is the same degree of sin as adultery in God’s eyes. If thinking about a woman sexually is sin, then obviously actually having sex with her would be sin.
In summary, there is absolutely no orthodox Christian group or teaching in history that has held the view that sex outside of the marriage covenant is acceptable to God. Only the most immature and untaught believer could think that, and if he were a true believer he would repent immediately when reading those verses, and would not try to justify the sin in any way.
The way true believers conduct themselves is in purity. The standard for all Christians is that “not even a hint” of sexual immorality be mentioned among us, let alone acted on!
Eph 5:3 But sexual immorality and all impurity or covetousness must not even be named among you, as is proper among saints. 4 Let there be no filthiness nor foolish talk nor crude joking, which are out of place, but instead let there be thanksgiving. 5 For you may be sure of this, that everyone who is sexually immoral or impure, or who is covetous (that is, an idolater), has no inheritance in the kingdom of Christ and God.
On the other hand, sex in marriage is a glorious gift of God, and is to be enjoyed within the bounds of an unbreakable covenant, i.e. after the marriage vows have been made publically and legally ratified. Sex is not a sign of so-called commitment and love, it is a reward of actual legal and covenantal commitment and love.