Thomas Brooks emphasizes that even the best of saints are still sinners, but they do not indulge in or cherish sin as the unregenerate do. He illustrates the difference between sin in a regenerate person and sin in an unregenerate person, comparing it to poison in a man versus poison in a serpent. A godly man may struggle with many sins, but he does not have a beloved or cherished sin; instead, he is tormented by his sins and desires to be rid of them. Brooks encourages believers to recognize their struggle against sin and to seek God's help in overcoming it, as true Christians do not willingly submit to sin. Ultimately, he warns that those who habitually indulge in sin are in a state of spiritual danger.

A child of God may slip into a sin—as a sheep may slip into the mire. But he does not, and cannot wallow in sin—as the swine wallows in the mire. The best of saints are sinners, though the worst and weakest of saints do not indulge sin or cherish it; or make daily provision for it; or take daily pleasure and delight in sin; or habitually yield a willing and total subjection to the authority and commands of sin. There is as much difference between sin in a regenerate person—and sin in an unregenerate person, as there is between poison in a man—and poison in a serpent. Poison in a man is most offensive and burdensome, and he readily uses all remedies and antidotes to expel it and get rid of it. But poison in a serpent, is in its natural place, and is most pleasing and delightful. Just so, sin in a regenerate man is most offensive and burdensome, and he readily uses all holy means and antidotes to expel it and to get rid of it. But sin in an unregenerate man is most pleasing and delightful, it being in its natural place. A godly man may have many sins—yet he has not one beloved sin, one bosom sin, one darling sin. His sins are his greatest grief and torment. Every godly man . . . hates all known sin, would sincerely have his sins not only pardoned, but destroyed, groans under the burden of sin, combats and conflicts with all known sin, has fixed purposes and designs not to sin, has a sincere willingness to be rid of all sin. No sincere Christian indulges himself in any trade, course, or way of sin. "Oh," says the gracious soul, "that I could be rid of . . . this proud heart, this hard heart, this unbelieving heart, this unclean heart, this earthly heart, this froward heart of mine!" O sirs, this is most certain—whoever gives up himself freely, willingly, cheerfully, habitually—to the service of any one particular lust or sin—he is in the state of nature, under wrath, and in the way to eternal ruin!