Thomas Shepard preaches about the reasons why men tend to rely on their own efforts and good works for salvation instead of fully trusting in Jesus Christ. He explains that this reliance on duties is rooted in human nature, ignorance of Christ's righteousness, the desire for self-comfort and self-righteousness, and the ability to hide one's sins behind religious activities. Shepard warns against resting in duties as a false sense of security, emphasizing that true salvation comes only through faith in Christ, not through our own works.

Now, the reasons why men rest in their duties are these:— First. Because it is natural to a man out of Christ to do so. Adam and all his posterity were to be saved by his doing: "Do this and live;" work, and here is your wages; win life, and wear it. Hence all his posterity seeks to this day to be saved by doing; like father, like son. Now, to come out of all duties truly to Christ, is a course hardly to be expected from a corrupt nature; hence men seek to find something in themselves. Now, as it is with a bankrupt, when his stock is spent, and his estate cracked, before he will work for wages, or live upon another, he will turn peddler of small wares, and so follow his old trade with a less stock: so men naturally follow their old trade of doing, and hope to get their living that way; and hence men, having no experience of trading with Christ by faith, live of themselves. Samson, when all his strength was lost, would go to shake himself as at other times: so when men's strength is lost, and God and grace are lost, yet men will go and try how they can live by shifts and working for themselves still. Secondly. Because men are ignorant of Jesus Christ and his righteousness; hence men can not go unto him, because they see him not; hence they shift as well as they can for themselves by their duties. Men seek to save themselves by their own swimming, when they see no rope cast out to help them. Thirdly. Because this is the easiest way to comfort the heart, and pacify conscience, and to please God, as the soul thinks; because by this means a man goes no farther than himself. Now, in forsaking all duties, a soul goes to heaven quite out of himself, and there he must wait many a year, and that for a little, it may be. Now, if a fainting man has medicine at his bed's head, he will not go to the shopkeeper for it. Men that have a balm of their own to heal them will not go to the physician. Fourthly. Because by virtue of these duties a man may hide his sin, and live quietly in his sin, yet be accounted an honest man, as the whore in Prov. 7:15, 16, having performed her vows, can entice without suspicion of men or check of conscience: so the scribes and Pharisees were horribly covetous, but their long prayers covered their deformities, (Matt. 23:14;) and hence men set their duties at a higher value than they are worth, thinking they shall save them because they are so useful to them. Good duties, like new apparel on a man pursued with hue and cry of conscience, keep him from being known. Take heed of resting in duties; good duties are men's money, without which they think themselves poor and miserable; but take heed that you and your money perish not together. (Gal. 5:3.) The paths to hell are but two. The first is the path of sin, which is a dirty way. Secondly, the path of duties, which (rested in) is but a clearer way. When the Israelites were in distress, (Judges 10:14,) the Lord bids them go to the gods they served: so when you shall lie howling on your death bed, the Lord will say, Go unto the good prayers and performances you nave made, and the tears you have shed. O, they will be miserable comforters at that day. Objection. But I think you will say, no true Christian man hopes to be saved by his good works and duties, but only by the mercy of God and merits of Christ. Answer. It is one thing to trust to be saved by duties, another thing to rest in duties. A man trusts unto them when he is of this opinion, that only good duties can save him. A man rests in duties when he is of this opinion, that only Christ can save him, but in his practice he goes about to save himself. The wisest of the Papists are so at this day, and so are our common Protestants. And this is a great subtlety of the heart, that is, when a man thinks he can not be saved by his good works and duties, but only by Christ: he then hopes, because he is of this opinion, that when he has done all he is an unprofitable servant; (which is only an act or work of the judgment informed aright;) that, therefore, because he is of this opinion, he shall be saved.