In short, God’s instructions are written because He loves humans. We wouldn’t think of operating a complex piece of machinery without some instruction on how to use it. And like any good manufacturer, God has given us an “instruction book” that tells us how to live in a way that will bring the best results.
Different cultures have established various customs over the centuries with regard to kissing. For example, in Old Testament times it was customary for family members to kiss each other, much as it is in many cultures today. In fact, the first reference to kissing in the Bible is in Genesis 27:26 when Isaac asked his son Jacob to come kiss him. Many cultures today continue the practice of what might be called a “peck on the cheek” as a sign of affection between family members. Since this is recorded so often in the Bible, it is obvious God is not against this display of family closeness.
It is also fairly generally recognized that a kiss on the lips—especially a long kiss—is a part of sexual activity and tends to arouse feelings of desire for closer intimacy. Once this type of kissing begins, there is a natural progression toward wanting to touch and caress further and ultimately toward full sexual intimacy. God designed this human response for the purpose of helping bond people together within marriage. Modern sex researchers have described what they call a “pleasure bond” that is formed during sexual intimacy. They have also discovered that this bond exists only within a monogamous relationship. The Bible describes this as a beautiful part of what God desires within marriage. See Proverbs 5:15-20 for example, which warns against sexual involvement with someone other than your spouse.
When sex is used outside of marriage, as it is so often today, God calls it fornication (if the person is not married) or adultery (if the person is married). Either way it is against God’s instructions. In the New Testament, the apostle Paul put it this way: “Flee sexual immorality. Every sin that a man does is outside the body, but he who commits sexual immorality sins against his own body. Or do you not know that your body is the temple of the Holy Spirit who is in you, whom you have from God, and you are not your own? For you were bought at a price; therefore glorify God in your body and in your spirit, which are God’s” (1 Corinthians 6:18-20).
Since Christians belong to God, they are expected to keep themselves pure sexually, which means they should only engage in sex within marriage. Kissing is often the starting point for getting involved in sexual relations because once you begin, there are very powerful hormones and desires that are awakened that sometimes overpower the mind and lead people to sexual intimacy. Again, when sex is done outside of marriage, God calls it sin.
So while God does not specifically give detailed instructions about kissing, it is clear from His instructions that passionate kissing does not belong outside of marriage, regardless of our background.