Does it feel sinful? Does it cause either one of you to have sexual thoughts? Does it sexually arouse either one of you? Does it make either one of you feel guilty afterwards? I don't honestly believe the actual sleeping together part is sinful. I think lying down and being pressed up against one another's bodies is sinful because there's almost no way that wouldn't be somewhat arousing. Also, as Clay wonderfully put, one small thing leads to another. Pretty soon you'll be justifying taking naps with little clothing on. After that becomes less than thrilling it will be napping while undressed. After that...you get the picture. And I'm sorry, nobody "accidentally" spends the night. Sure, you can use that as an excuse but the question remains, why didn't anyone exercise discretion and say "ya know what? It's getting late. I should go home"?
That "feeling" is one of those feelings of "oneness" you should only experience with your spouse. The longer your "no big deal" list is before marriage, the shorter your "very special" list will be after marriage.
Christians, stop justifying your actions! We are not to crave the things of the world. Don't buy into the lies of satan that just because it "feels good" means it's okay! Don't buy into the lie that you two can control yourselves and not go "all the way"! What good is "technical" sexual purity when God asks us to give Him our entire body? Don't buy into the lie that it's acceptable to engage in these acts before marriage. Brothers and sisters in Christ you are being deceived by satan.
