A godly man does not indulge in any sin
(from Thomas Watson's "The Godly Man's Picture")

Though sin lives in him—yet he does not live in sin. A godly man may step into sin through infirmity—but he does not keep on that road. He prays, "Search me, O God, and know my heart; test me and know my thoughts. Point out anything in me that offends you, and lead me along the path of everlasting life." (Psalm 139:24).
Question: What is it to indulge sin?
Answer 1: To give the breast to it and feed it. As a fond parent humors his child and lets him have what he wants, so to indulge sin is to humor sin.
Answer 2: To indulge sin is to commit it with delight. The ungodly "delight in wickedness" (2 Thess. 2:12).
In this sense, a godly man does not indulge sin. Though sin is in him, he is troubled at it and would gladly get rid of it. There is as much difference between sin in the wicked and sin in the godly—as between poison being in a serpent and poison being in a man. Poison in a serpent is in its natural place and is delightful—but poison in a man's body is harmful and he uses antidotes to expel it. So sin in a wicked man is delightful, being in its natural place—but sin in a child of God is burdensome and he uses all means to expel it. The sin is trimmed off. The will is against it. A godly man enters his protest against sin: "Oh, what a miserable person I am! Who will free me from this life that is dominated by sin?" (Romans 7:24). A child of God, while he commits sin, hates the sin he commits (Romans 7).
In particular there are four kinds of sin, which a godly man will not allow himself:
1. SECRET sins. Some are more modest than to commit open gross sin. That would be a stain on their reputation. But they will sit brooding upon sin in a corner: "Saul secretly practiced mischief" (1 Sam. 23:9). All will not sin on a balcony—but perhaps they will sin behind the curtain. Rachel did not carry her father's images like a saddle cloth to be exposed to public view—but she put them under her and sat on them (Gen. 31:34). Many carry their sins secretly.
But a godly man dare not sin secretly:
(1) He knows that God sees in secret, "for he knows the secrets of every heart." (Psalm 44:21). As God cannot be deceived by our subtlety, so he cannot be excluded by our secrecy.
(2) A godly man knows that secret sins are in some sense worse than others. They reveal more guile and atheism. The curtain-sinner makes himself believe that God does not see: "Son of man, have you seen what the leaders of Israel are doing with their idols in dark rooms? They are saying—The Lord doesn't see us!" (Ezek. 8:12). Those who have bad eyes think that the sun is dim. How it provokes God, that men's atheism should give the lie to his omniscience! "He who formed the eye, shall he not see?" (Psalm 94:9).
(3) A godly man knows that secret sins shall not escape God's justice. A judge on the bench can punish no offence but what is proved by witnesses. He cannot punish the treason of the heart—but the sins of the heart are as visible to God as if they were written upon the forehead. As God will reward secret duties, so he will revenge secret sins.
2. GAINFUL sins. Gain is the golden bait, with which Satan fishes for souls! "The sweet smell of money." This was the last temptation he used with Christ: "All these things will I give you" (Matt. 4:9). But Christ saw the hook under the bait. Many who have escaped gross sins, are still caught in a golden net. To gain the world, they will use indirect routes.
A godly man dare not travel for riches along the devil's highway. Those are sad gains, which make a man lose peace of conscience and heaven at last. He who gets an estate by injustice stuffs his pillow with thorns, and his head will lie very uneasy when he comes to die. "What good will it be for a man if he gains the whole world, yet forfeits his soul?" Matthew 16:26.
3. A beloved BESETTING sin. "Let us throw off everything that hinders and the sin that so easily entangles, and let us run with perseverance the race marked out for us." Hebrews 12:1. There is usually one sin that is the favorite—the sin which the heart is most fond of. A beloved sin lies in a man's bosom as the disciple whom Jesus loved, leaned on his bosom (John 13:23). A godly man will not indulge a darling sin: "I kept myself from my iniquity" (Psalm 18:23). "I will not indulge the sin of my constitution, to which the bias of my heart more naturally inclines." "Fight neither with small nor great—but only with the king" (1 Kings 22:31). A godly man fights this king sin. The oracle of Apollo answered the people of Cyrrha that if they would live in peace among themselves, they must make continual war with those strangers who were on their borders. If we would have peace in our souls, we must maintain a war against our favorite sin and never leave off until it is subdued.
Question: How shall we know what our beloved sin is?
Answer 1: The sin which a man does not love to have reproved is the darling sin. Herod could not endure having his incest spoken against. If the prophet meddles with that sin—it shall cost him his head! "Do not touch my Herodias!" Men can be content to have other sins reproved—but if the minister puts his finger on the sore, and touches this sin—their hearts begin to burn in malice against him!
Answer 2: The sin on which the thoughts run most, is the darling sin. Whichever way the thoughts go, the heart goes. He who is in love with a person cannot keep his thoughts off that person. Examine what sin runs most in your mind, what sin is first in your thoughts and greets you in the morning—that is your predominant sin.
Answer 3: The sin which has most power over us, and most easily leads us captive, is the one beloved by the soul. There are some sins which a man can better resist. If they come for entertainment, he can more easily put them off. But the bosom sin comes as a suitor, and he cannot deny it—but is overcome by it. The young man in the Gospel had repulsed many sins—but there was one sin which soiled him, and that was covetousness. Christians, mark what sin you are most readily led captive by—that is the harlot in your bosom! It is a sad thing that a man should be so bewitched by lust, that if it asks him to part with not only half the kingdom (Esther 7:2) but the whole kingdom of heaven, he must part with it, to gratify that lust!
Answer 4: The sin which men use arguments to defend, is the beloved sin. He who has a jewel in his bosom, will defend it to his death. So when there is any sin in the bosom, men will defend it. The sin we advocate and dispute for, is the besetting sin. If the sin is anger, we plead for it: "I do well to be angry" (Jonah 4:9). If the sin is covetousness and we vindicate it and perhaps wrest Scripture to justify it—that is the sin which lies nearest the heart.
Answer 5: The sin which most troubles us, and flies most in the face in an hour of sickness and distress, that is the Delilah sin! When Joseph's brethren were distressed, their sin in selling their brother came to remembrance: "We are truly guilty concerning our brother . . . therefore is this distress come upon us" (Gen. 42:21). So, when a man is on a sickbed and conscience says, "You have been guilty of such a sin; you went on in it, and rolled it like honey under your tongue!" Conscience is reading him a sad lecture. That was the beloved sin for sure.
Answer 6: The sin which a man finds most difficulty in giving up, is the endeared sin. Of all his sons, Jacob found most difficulty in parting with Benjamin. So the sinner says, "This and that sin I have parted with—but must Benjamin go, must I part with this delightful sin? That pierces my heart!" As with a castle that has several forts about it, the first and second fort are taken—but when it comes to the castle, the governor will rather fight and die than yield that. So a man may allow some of his sins to be demolished—but when it comes to one sin, that is the taking of the castle; he will never agree to part with that! That is the master sin for sure.

The besetting sin is a God-provoking sin. The wise men of Troy counseled Priam to send Helena back to the Greeks, not permitting himself to be abused any longer by the charms of her beauty, because keeping her within the city would lay the foundation of a fatal war. So we should put away our Delilah sin, lest it incense the God of heaven, and make him commence a war against us.
The besetting sin is, of all others, most dangerous. As Samson's strength lay in his hair, so the strength of sin, lies in this beloved sin. This is like a poison striking the heart, which brings death. A godly man will lay the axe of repentance to this sin and hew it down! He sets this sin, like Uriah, in the forefront of the battle, so that it may be slain. He will sacrifice this Isaac, he will pluck out this right eye, so that he may see better to go to heaven.
4. Those sins which the world counts LESSER. There is no such thing as little sin—yet some may be deemed less comparatively. But a godly man will not indulge himself in these. Such as:
(1) Sins of omission. Some think it no great matter to omit family, or private prayer. They can go for several months and God never hears from them. A godly man will as soon live without food, as without prayer. He knows that every creature of God is sanctified by prayer (1 Tim. 4:5). The bird may shame many Christians; it never takes a drop—but the eye is lifted up towards heaven.
(2) A godly man dares not allow himself vain, frothy discourse, much less that which looks like an oath. If God will judge for idle words, will he not much more for idle oaths?
(3) A godly man dare not allow himself rash censuring. Some think this a small matter. They will not swear—but they will slander. This is very evil. This is wounding a man in that which is dearest to him. He who is godly turns all his censures upon himself! He judges himself for his own sins—but is very watchful and concerned, about the good name of another.
Use: As you would be numbered among the genealogies of the saints—do not indulge yourselves in any sin. Consider the mischief which one sin lived in, will do:
1. One sin lived in, gives Satan as much advantage against you as more sins. The fowler can hold a bird by one wing. Satan held Judas fast by one sin.
2. One sin lived in, proves that the heart is not sound. He who hides one rebel in his house is a traitor to the crown. The person who indulges one sin is a traitorous hypocrite.
3. One sin lived in, will make way for more, as a little thief can open the door to more. Sins are linked and chained together. One sin will draw on more. David's adultery made way for murder. One sin never goes alone! If there is only one nest egg—the devil can brood on it.
4. One sin lived in, is as much a breach of God's law as more sins. "Whoever keeps the entire law, yet fails in one point, is guilty of breaking it all" (Jas. 2:10). The king may make a law against felony, treason and murder. If a man is guilty of only one of these, he is a transgressor.
5. One sin lived in, prevents Christ from entering. One stone in the pipe keeps out the water. One sin indulged in, obstructs the soul and keeps the streams of Christ's blood from running into it.
6. One sin lived in, will spoil all your good duties. A drop of poison will spoil a glass of wine. Abimelech, a bastard-son, destroyed seventy of his brethren (Judges 9:5). One bastard-sin will destroy seventy prayers. One dead fly will spoil the whole box of precious ointment.
7. One sin lived in will be a cankerworm to eat out the peace of conscience. It takes away the manna from the ark, and leaves only a rod. "Alas! What a scorpion lies within!" (Seneca). One sin is a pirate—to rob a Christian of his comfort. One jarring string puts all the music out of tune. One sin lived in—will spoil the music of conscience.
8. One sin lived in, will damn as well as more sins. One disease is enough to kill. If a fence is made ever so strong, and only one gap is left open; the wild beast may enter and tread down the corn. If only one sin is allowed in the soul, you leave open a gap for the devil to enter! A soldier may have only one gap in his armor--and the bullet may enter there. He may as well be shot there--as if he had no armor on at all. So if you favor only one sin, you leave a part of your soul unprotected--and the bullet of God's wrath may enter there—and shoot you! One sin lived in, may shut you out of heaven! What difference is there, between being shut out of heaven for one sin--or for many sins? One millstone will sink a man into the sea--as well as a hundred!
9. One sin harbored in the soul will unfit us for suffering. How soon an hour of trial may come. A man who has hurt his shoulder cannot carry a heavy burden, and a man who has any guilt in his conscience cannot carry the cross of Christ. Will he who cannot deny his lust for Christ—deny his life for Christ? One unmortified sin in the soul—will bring forth the bitter fruit of apostasy.
If, then, you would show yourselves godly, give a certificate of divorce to every sin. Kill the Goliath sin! "Let not sin reign" (Romans 6:12). In the original it is "Let not sin king it over you." Grace and sin may be together—but grace and the love of sin cannot. Therefore parley with sin no longer—but with the spear of mortification, spill the heart-blood of every sin! "For if you live after the flesh, you shall die: but if you through the Spirit do mortify the deeds of the body, you shall live." Romans 8:13. "So put to death the sinful, earthly things lurking within you." Colossians 3:5.