Flee fornication Every sin, etc. Having set before us honorable conduct, he now shows how much we ought to abhor fornication, setting before us the enormity of its wickedness and baseness. Now he shows its greatness by comparison -- that this sin alone, of all sins, puts a brand of disgrace upon the body. The body, it is true, is defiled also by theft, and murder, and drunkenness, in accordance with those statements -- Your hands are defiled with blood. (Isaiah 1:15.) You have yielded your members instruments of iniquity unto sin, (Romans 6:19,) and the like. Hence some, in order to avoid this inconsistency, understand the words rendered against his own body, as meaning against us, as being connected with Christ; but this appears to me to be more ingenious than solid. Besides, they do not escape even in this way, because that same thing, too, might be affirmed of idolatry equally with fornication. For he who prostrates himself before an idol, sins against connection with Christ. Hence I explain it in this way, that he does not altogether deny that there are other vices, in like manner, by which our body is dishonored and disgraced, but that his meaning is simply this -- that defilement does not attach itself to our body from other vices in the same way [1] as it does from fornication My hand, it is true, is defiled by theft or murder, my tongue by evil speaking, or perjury, [2] and the whole body by drunkenness; but fornication leaves a stain impressed upon the body, such as is not impressed upon it from other sins. According to this comparison, or, in other words, in the sense of less and more, other sins are said to be without the body -- not, however, as though they do not at all affect the body, viewing each one by itself.

Footnotes

1 - "N'en demeure point tellement imprimee en nostre corps;" -- "Does not remain impressed upon our body in the same way."

2 - "Par mesdisance, detraction, et periure;" -- "By evil-speaking, detraction, and perjury."

Flee fornication - A solemn command of God - as explicit as any that thundered from Mount Sinai. None can disregard it with impunity - none can violate it without being exposed to the awful vengeance of the Almighty. There is force and emphasis in the word "flee" φεύγατε pheugate. Man should escape from it; he should not stay to reason about it; to debate the matter; or even to contend with his propensities, and to try the strength of his virtue. There are some sins which a man can resist; some about which he can reason without danger of pollution. But this is a sin where a man is safe only when he flies; free from pollution only when he refuses to entertain a thought of it; secure when he seeks a victory by flight, and a conquest by retreat. Let a man turn away from it without reflection on it and he is safe. Let him think, and reason, and he may be ruined. "The very passage of an impure thought through the mind leaves pollution behind it." An argument on the subject often leaves pollution; a description ruins; and even the presentation of motives against it may often fix the mind with dangerous inclination on the crime. There is no way of avoiding the pollution but in the manner prescribed by Paul; there is no man safe who will not follow his direction. How many a young man would be saved from poverty, want, disease, curses, tears, and hell, could these two words be made to blaze before him like the writing before the astonished eyes of Belshazzar Daniel. 5, and could they terrify him from even the momentary contemplation of the crime.
Every sin - This is to be taken comparatively. Sins in general; the common sins which people commit do not immediately and directly affect the body, or waste its energies, and destroy life. Such is the case with falsehood, theft, malice, dishonesty, pride, ambition, etc. They do not immediately and directly impair the constitution amid waste its energies.
Is without the body - Does not immediately and directly affect the body. The more immediate effect is on the mind; but the sin under consideration produces an immediate and direct effect on the body itself.
Sinneth against his own body - This is the FourTH argument against indulgence in this vice; and it is more striking and forcible. The sense is, "It wastes the bodily energies; produces feebleness, weakness, and disease; it impairs the strength, enervates the man, and shortens life." Were it proper, this might be proveD to the satisfaction of every man by an examination of the effects of licentious indulgence. Those who wish to see the effects stated may find them in Dr. Rush on the Diseases of the Mind. Perhaps no single sin has done so much to produce the most painful and dreadful diseases, to weaken the constitution, and to shorten life as this. Other vices, as gluttony and drunkenness, do this also, and all sin has some effect in destroying the body, but it is true of this sin in an eminent degree.

Flee fornication - Abominate, detest, and escape from every kind of uncleanness. Some sins, or solicitations to sin, may be reasoned with; in the above cases, if you parley you are undone; reason not, but Fly!
Sinneth against his own body - Though sin of every species has a tendency to destroy life, yet none are so mortal as those to which the apostle refers; they strike immediately at the basis of the constitution. By the just judgment of God, all these irregular and sinful connections are married to death. Neither prostitutes, whoremongers, nor unclean persons of any description, can live out half their days. It would be easy to show, and prove also, how the end of these things, even with respect to the body, is death; but I forbear, and shall finish the subject with the words of the prophet: The show of their countenance doth witness against them, and they declare their sin as Sodom, they hide it not; wo unto their soul, for they have rewarded evil unto themselves.

(13) Flee fornication. Every sin that a man doeth is without the body; but he that committeth fornication sinneth against his own body.
(13) Another argument why fornication is to be avoided, because it defiles the body with a peculiar type of filthiness.

Flee fornication,.... As that which is hurtful, scandalous, and unbecoming Christians; avoid it, and all the occasions of it, that may lead unto it, and be incentives of it:
every sin that a man doth is without the body not but that other sins are committed by the body, and by the members of it as instruments; they are generally committed by the abuse of other things that are without, and do not belong to the body; and so do not bring that hurt unto and reproach upon the body, as fornication does:
but he that committeth fornication, sinneth against his own body; not meaning his wife, which is as his own body; but his proper natural body, which is not only the instrument by which this sin is committed, but the object against which it is committed; and which is defiled and dishonoured by it; and sometimes its strength and health are impaired, and it is filled with nauseous diseases hereby.

Flee--The only safety in such temptations is flight (Genesis 39:12; Job 31:1).
Every sin--The Greek is forcible. "Every sin whatsoever that a man doeth." Every other sin; even gluttony, drunkenness, and self-murder are "without," that is, comparatively external to the body (Mark 7:18; compare Proverbs 6:30-32). He certainly injures, but he does not alienate the body itself; the sin is not terminated in the body; he rather sins against the perishing accidents of the body (as the "belly," and the body's present temporary organization), and against the soul than against the body in its permanent essence, designed "for the Lord." "But" the fornicator alienates that body which is the Lord's, and makes it one with a harlot's body, and so "sinneth against his own body," that is, against the verity and nature of his body; not a mere effect on the body from without, but a contradiction of the truth of the body, wrought within itself [ALFORD].

Flee fornication. The sin must be fled. The way to avoid it is to avoid temptation. We must conquer by running away. Thus it was that Joseph prevailed.
Every sin . . . is without the body. The temptations come from without and assail the man through the senses. This is the rule in the case of sin. It is not said of fornication that it is not stimulated without, or that it, alone of sins, assails the body, but that it is peculiarly a sin against the body. It defiles a body which is designed to be a member of Christ, and a temple of the Holy Spirit; separates it from the union with Christ, and unites it with a harlot. The grievousness of the sin is in the desecration to such an unholy purpose of a body which has become a member of Christ, a part of the temple of God.
What? know ye not that your body, etc. This makes clear how terrible is the sin of defiling the body by licentiousness. It is desecrating God's temple. As the Shekinah dwelt in the temple of Israel, so the Holy Spirit in Christ's temple, which we are.
Ye are not your own. But members of Christ, and hence have not the right to use our bodies to our own pleasure.
Ye are bought with a price. Christ paid the price, even his blood. Hence, since both body and spirit are God's, both should be used to glorify him. The fact that we are his, purchased, parts of his spiritual temple, makes the obligation imperative to consecrate the body and spirit to his service.

Flee fornication - All unlawful commerce with women, with speed, with abhorrence, with all your might. Every sin that a man commits against his neighbour terminates upon an object out of himself, and does not so immediately pollute his body, though it does his soul. But he that committeth fornication, sinneth against his own body - Pollutes, dishonours, and degrades it to a level with brute beasts.