I regularly get searches coming to this site like the following one:
This sort of thing is thrown around so often that I think a lot of people must think it's at least close to the truth. I even thought it was almost true for a while. It's actually not close to the truth, not in the slightest. Premarital sex was extremely uncommon in ancient Israel compared to today, and it thus doesn't come out anywhere near as explicitly in the more emphatic commands, but there's enough reason to think the laws of Israel condemned it very strongly in the few kinds of circumstances when it did have something to say about it. Since the new covenant commands against sexual immorality would have been assumed to rely on the Torah for what constitutes sexual immorality, Christians who follow the New Testament therefore ought to see sexual immorality as including premarital sex.
If it were viewed as perfectly ok, why is there a requirement that someone who sleeps with an unmarried woman would have to compensate her with a bride-price, whether her father consents to let him marry her or not? (Exodus 22:16-17) While some of the requirements for Levites serving in the tabernacle and temple were elevated beyond other Israelites (e.g. no deformities), the command to marry a virgin is grounded in the principle that he not profane his children (Leviticus 21:13-15), which suggests there's at least something less than perfect about such a marriage. Deuteronomy 22 treats premarital sex as tantamount to prostitution, and though the law only has a penalty for the woman that's likely because women can establish virginity in ways that men can't. (Besides, going to a prostitute is a sin just as much as being a prostitute is, and if it's prostitution then he's guilty and not just her.)
Now people are free to reject biblical teachings as a guide for how we ought to live. By and large contemporary Western society has done that. But I don't think those who accept the Bible as authoritative can get away with the sort of claim this person was searching for. The Bible doesn't always cooperate with our attempts to make it say what we want it to say. There may be some complex hermeneutical gymnastics someone could come up with to get around this, but it's not something that should come very obviously, and it seems to me that sort of thing will largely be driven by what someone would want the Bible to say rather than by what the biblical text should lead people to conclude.