The following is an excerpt from The MacArthur New Testament Commentary on 1 Corinthians 6.

SEXUAL SIN HARMSAll things are lawful for me, but not all things are profitable. (6:12a)The statement, All things are lawful may have been a common Corinthian saying in that liberated society. Paul borrows it and, playing off it, says, “It is so for me, too. Every sin I as a Christian commit is forgiven in Jesus Christ.” But no sin is ever right or good, and no sin ever produces anything right or good. Sin can never be worthwhile or profitable. Profitable (sumphero) means “to be to advantage.” In the sense that believers are free and no longer under the penalty of the law in any way, all things are lawful for them. But the price for doing some things is terribly high, terribly unprofitable. Sin never brings profit; it always brings loss.

The particular type of sin Paul has in mind here (vv. 13–20) is sexual sin. No sin that a person commits has more built–in pitfalls, problems, and destructiveness than sexual sin. It has broken more marriages, shattered more homes, caused more heartache and disease, and destroyed more lives than alcohol and drugs combined. It causes lying, stealing, cheating, and killing, as well as bitterness, hatred, slander, gossip, and unforgivingness.

The dangers and harm of sexual sin are nowhere presented more vividly and forcefully than in Proverbs. “The lips of an adulteress drip honey, and smoother than oil is her speech” (Prov. 5:3). The basic truth applies to a prostitute or to any other woman who tries to seduce a man. It also applies to a man who tries to seduce a woman. The point is that sexual allurement is extremely enticing and powerful. It seems nice, enjoyable, and good. It promises nothing but pleasure and satisfaction. But what it ends up giving “is bitter as wormwood, sharp as a two–edged sword. Her feet go down to death, her steps lay hold of Sheol. She does not ponder the path of life; her ways are unstable, she does not know it” (vv. 4–6). The first characteristic of sexual sin is deceit. It never delivers what it promises. It offers great satisfaction but gives great disappointment. It claims to be real living but is really the way to death. Illicit sexual relationships are always “unstable.” Nothing binds those involved except the temporary and impersonal gratification of physical impulses. That is poor cement. Another tragedy of sexual sin is that often those involved do “not know it” is unstable, do not realize perhaps for a long time that their relationship cannot be lasting. Thus they fall deeper and deeper into the pit of their doomed relationship, which makes the dissolution all the more devastating and painful.

Those who consider all sex to be basically evil, however, are as far from the truth as those who consider all sex to be basically good and permissible. God is not against sex. He created and blessed it. When used exclusively within marriage, as the Lord intends, sex is beautiful, satisfying, and stabilizing. “Let your fountain be blessed,” Scripture says, “and rejoice in the wife of your youth. … Be exhilarated always with her love” (Prov. 5:18–19).

The Bible’s advice for avoiding sexual involvement outside marriage is simple: stay as far away as possible from the persons and places likely to get you in trouble.“Keep your way far from her, and do not go near the door of her house” (Prov. 5:8). When repeatedly enticed by Potiphar’s wife, Joseph refused not only “to lie beside her” but even to “be with her” (Gen. 39:10). When she tried to force him into adultery and grabbed his coat, “he left his garment in her hand and fled, and went outside” (v. 12). It was not the time for argument or explanation but for flight. When we unavoidably get caught in such a situation, the only sensible thing to do is to get away from it as quickly as we can. Passion is not rational or sensible, and sexually dangerous situations should be avoided or fled, not debated.

Involvement in illicit sex leads to loss of health, loss of possessions, and loss of honor and respect. Every person who continues in such sins does not necessarily suffer all of those losses, but those are the types of loss that persistent sexual sin produces. The sex indulger will come to discover that he has lost his “years to the cruel one,” that his “hard–earned goods” have gone “to the house of an alien,” and that he will “groan” in his latter years and find his “flesh and [his] body are consumed” (Prov. 5:9–11). The “stolen water” of sexual relations outside of marriage “is sweet; and bread eaten in secret is pleasant”; but “the dead are there” (Prov. 9:17–18). Sexual sin is a “no win” situation. It is never profitable and always harmful.

God looks on sexual immorality with extreme seriousness. Because of this sin in Israel, “twenty–three thousand fell in one day” (1 Cor. 10:8). David was a man after God’s own heart and was greatly used of the Lord in leading Israel and even in writing Scripture. But David was not exempted from the consequences of his sin. He committed adultery with Bathsheba and she became pregnant. He then arranged for her husband to be killed in battle and took her as his own wife. “But the thing that David had done was evil in the sight of the Lord” (2 Sam. 11:27). Through His prophet Nathan, God told David that because of his sin, “the sword shall never depart from your house. … I will raise up evil against you from your own household,” and “the child also that is born to you shall surely die” (12:10–11, 14). David paid for those sins almost every day of his life. Several of his sons were rebellious, jealous, and vengeful, and his family life was for the most part a tragic shambles.

David repented and was forgiven. “The Lord also has taken away your sin” (12:13), but the Lord did not take away the consequences of the sin. After that experience the king wrote Psalm 51, in gratitude but also in deep remorse and agony. He had experienced God’s marvelous and gracious forgiveness, but he had also come to see the awfulness of his sin. “Against Thee, Thee only, I have sinned, and done what is evil in Thy sight” (v. 4). God’s grace is free, but the cost of sin is high.

SEXUAL SIN CONTROLSAll things are lawful for me, but I will not be mastered by anything. (6:12b)Paul was free in the grace of Christ to do as he pleased, but he refused to allow himself to be mastered by anything or anyone but Christ. He would not become enslaved to any habit or custom and certainly not to any sin. “For sin shall not be master over you, for you are not under law, but under grace” (Rom. 6:14).

No sin is more enslaving than sexual sin. The more it is indulged, the more it controls the indulger. Often it begins with small indiscretions, which lead to greater ones and finally to flagrant vice. The progression of sin is reflected in Psalm 1: “Blessed is the man who does not walk in the counsel of the wicked, nor stand in the path of sinners, nor sit in the seat of scoffers” (v. 1). When we willingly associate with sin, we will soon come to tolerate it and then to practice it. Like all other sins that are not resisted, sins of sex will grow, and eventually they will corrupt and destroy not only the persons directly involved but many innocent persons besides.

The Corinthians were no strangers to sins of sex, and unfortunately many believers there had gone back to them. In the name of Christian freedom they had become controlled by their own fleshly desires.

Paul wrote the Thessalonians, “For this is the will of God, your sanctification; that is, that you abstain from sexual immorality; that each of you know how to possess his own vessel in sanctification and honor, not in lustful passion, like the Gentiles who do not know God” (1 Thess. 4:3—5). The context argues that “vessel” is here a synonym for body rather than for wife, as many interpreters hold. Every believer is to rightly possess, rightly control, his own body. If we are living in the Spirit, we “are putting to death the deeds of the body” (Rom. 8:13).

It is not as easy to be in control of ourselves as we sometimes think. Many people are deceived in thinking they are perfectly in control of their thoughts and actions, simply because they always do what they want. The fact, however, is that their desires and passions are telling them what to do, and they are going along. They are not masters of their desires, but are willing slaves. Their flesh is controlling their minds.
Paul himself testifies that he had to “buffet [his] body and make it [his] slave, lest possibly, after [he had] preached to others, [he himself] should be disqualified” (1 Cor. 9:27). Buffet (hupopiazo) means literally, “to give a black eye, or to beat the face black and blue.” To keep his body from enslaving him, he had to enslave his body. Otherwise he could become disqualified, not for salvation but for holy living and useful service to God.
SEXUAL SIN PERVERTSSexual sin not only harms and controls but also perverts. It especially perverts God’s plan and purpose for the bodies of His people. A Christian’s body is for the Lord; it is a member of Christ; and it is the temple of the Holy Spirit.