Does the Bible say much about sexual desire? Where is this permissible and where is it not, according to the Bible?
Rightful Sexual Desire
Within the confines of marriage, there is absolutely nothing sinful about having sexual desire for a spouse. The Bible actually encourages us to have this when it says “Let her breasts fill you at all times with delight; be intoxicated always in her love” (Prov 5:18-19) but we also see a warning in the form of a question, “Why should you be intoxicated, my son, with a forbidden woman and embrace the bosom of an adulteress” (Prov 5:20)? His sage advice is to “Enjoy life with the wife whom you love, all the days of your vain life that he has given you under the sun, because that is your portion in life and in your toil at which you toil under the sun” (Eccl 9:9). The point is that God created us as sexual beings but also as being responsible for our moral and immoral behavior and God will not hold those guiltless who live in sexual immorality  so “Let marriage be held in honor among all, and let the marriage bed be undefiled, for God will judge the sexually immoral and adulterous” (Heb 13:4).
Wrong Sexual Desire
Jesus tells us that it’s not just the physical act of sexual immorality but even lusting after someone in our heart is considered adultery as He explains, “You have heard that it was said, ‘You shall not commit adultery.’ But I say to you that everyone who looks at a woman with lustful intent has already committed adultery with her in his heart” (Matt 5:27-28) but He also says to “everyone who divorces his wife, except on the ground of sexual immorality, makes her commit adultery, and whoever marries a divorced woman commits adultery” (Matt 5:32). The Apostle Paul adds that “The body is not meant for sexual immorality, but for the Lord, and the Lord for the body” (1 Cor 6:13) and so he asks, “Do you not know that your bodies are members of Christ? Shall I then take the members of Christ and make them members of a prostitute? Never! Or do you not know that he who is joined to a prostitute becomes one body with her? For, as it is written, “The two will become one flesh” (1 Cor 6:15-16) and so he gives us all life and death advice; “Flee from sexual immorality. Every other sin a person commits is outside the body, but the sexually immoral person sins against his own body” (1 Cor 6:18). Rather than glorifying God in our body, we can bring the judgment of God on us who refuse to repent of this sin.
God’s Judgment on the Sexually Immoral
God does not compromise with sexual immorality and sexual immorality includes sex outside of marriage and adultery or having sex with someone who’s not our spouse. Even if a person is engaged, they are not married and have no excuse for having sex before marriage. God gives no allowance for such sinful behavior. Those who say that they are Christian and yet are living with someone are deceiving themselves as the Apostle John warns, “let no one deceive you. Whoever practices righteousness is righteous, as he is righteous. Whoever makes a practice of sinning is of the devil, for the devil has been sinning from the beginning” (1 John 3:7-8). His conclusion is that “No one born of God makes a practice of sinning, for God’s seed abides in him, and he cannot keep on sinning because he has been born of God. By this it is evident who are the children of God, and who are the children of the devil: whoever does not practice righteousness is not of God, nor is the one who does not love his brother” (1 John 3:9-10). If a person says “If you really loved me you would have sex with me” but that’s the exact opposite of what love really is because love does no harm to another and never takes advantage of someone by having sex with them outside of marriage. All they are doing is using another person to fulfill their own lustful desires and that is not love…that is sin. In truth, it is loving someone when we keep ourselves free from sexual immorality and wait for the consummation of the marriage and not take advantage of someone.
Who Enters the Kingdom?
The command to abstain from sexual immorality is nothing new to the New Testament as the Book of Leviticus  commands, “And you shall not lie sexually with your neighbor’s wife and so make yourself unclean with her” (Lev 18:20) and comes with a deadly serious warning that “he (or she) who goes in to his neighbor’s wife; none who touches her will go unpunished” (Prov 6:29). Can a person who is living in a state of sexual immorality have the hope of entering the kingdom if they continue to live in this sinful lifestyle? No, because Paul warns “Or do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived: neither the sexually immoral, nor idolaters, nor adulterers, nor men who practice homosexuality” (1 Cor 6:9). Caving into temptation and finding oneself living in a continual state of sexual immorality is very bad news because all who refuse to turn away from it reveal that they are living in the flesh and “the works of the flesh are evident: sexual immorality, impurity, sensuality, idolatry, sorcery, enmity, strife, jealousy, fits of anger, rivalries, dissensions, divisions, envy, drunkenness, orgies, and things like these. I warn you, as I warned you before, that those who do such things will not inherit the kingdom of God” (Gal 5:19-21).
Paul makes it clear that “those who belong to Christ Jesus have crucified the flesh with its passions and desires” (Gal 5:24) and those who don’t, may not belong to Christ at all. No one is sinless but repeated or ongoing sexual immorality will lead to a final, fatal ending that is worse than can be described. The Apostle John concludes by adding that “the cowardly, the faithless, the detestable, as for murderers, the sexually immoral, sorcerers, idolaters, and all liars, their portion will be in the lake that burns with fire and sulfur, which is the second death” (Rev 21:8). If someone says that God is a God of love and that they’re God wouldn’t send someone to hell, tell them, “Yes, you’re right…your god would never do that because he doesn’t exist.” Tell them that God’s love doesn’t nullify His laws nor does it do away with the consequences and God will not leave unpunished who do such things nor will He allow them into the kingdom for no unclean thing will be found in the New Jerusalem (Rev 21:27).
Related reading: Sex Outside of Marriage 
Resource – Scripture quotations are from The Holy Bible, English Standard Version® (ESV®), copyright © 2001 by Crossway, a publishing ministry of Good News Publishers. Used by permission. All rights reserved.