Practically every book in the New Testament warns about the danger of sexual immorality and God makes it absolutely clear He expects Christians to take steps to ‘flee’ or avoid sexual temptation.
In Genesis chapter 2 God reveals He created humanity as male and female and established the marriage relationship. “And the Lord God said, “It is not good that man should be alone; I will make him a helper comparable to him…Therefore a man shall leave his father and mother and be joined to his wife, and they shall become one flesh” (Genesis 2:18, 24).
Our Creator makes it clear to Adam and Eve right after they were created He intended a man and a woman to form a separate household with their primary loyalty to each other. “One flesh” means a devoted and permanent partnership in which the husband and wife draw ever-closer physically, mentally and spiritually -- and God meant regular sexual relations to be included in the marriage relationship in order to foster that intimacy (1 Corinthians 6:16-20; 7:2-4).
An extremely important part of our character is how we rule over our sexuality. Any sexual relations or activities outside of marriage are sinful as they break God’s laws, pollute the sanctity of marriage and harm us physically, mentally, emotionally and spiritually. In addition such behaviour blasphemes the profound portrayal of the marriage of Jesus Christ with the Church (1 Corinthians 6:9-18; Ephesians 5:25-33; Revelation 19:7-9) which physical marriage is meant to symbolise.
Remaining morally pure means much more than just not “going all the way”, but includes what is called necking, petting or making out. God instituted marriage and to protect the blessedness of marriage, the Bible specifically warns against extramarital sex (adultery), premarital sex (fornication), incest, prostitution and other sexual behaviour.
But biblical instruction goes further than just physically avoiding sexual temptation. Jesus Christ made it clear in the Sermon on the Mount (Matthew 5 through 7) we must obey God in the spirit of the law as well. “You have heard that it was said to those of old, ‘You shall not commit adultery.’ But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart” (Matthew 5:27-28).
Christ is telling us that lust also extends to our thoughts, even when we might not be actually looking at a member of the opposite sex. This instruction is especially applicable in the 21st century, as modern technology has provided even more opportunities to sin with pornography being easily brought into the home via the Internet.