Thomas Brooks warns against the deceptive nature of sin, emphasizing that Satan disguises sin with the appearance of virtue to lead us astray. He illustrates that sin remains vile and abominable, regardless of how it is presented, much like a poisonous pill gilded in gold or a wolf in sheep's clothing. Brooks urges believers to recognize the true nature of sin, which can often be hidden beneath attractive exteriors, and to remain vigilant against its allure.

"Lest Satan should get an advantage of us: for we are not ignorant of his devices." 2 Corinthians 2:11 Satan knows that if he would present sin in its own nature and dress, the soul would rather fly from it than yield to it; and therefore he presents it unto us, not in its own proper colors—but painted and gilded over with the name and show of virtue, that we may the more easily be overcome by it, and take the more pleasure in committing of it. Consider that sin is never a whit the less filthy, vile, and abominable—by its being colored and painted with virtue's colors. A poisonous pill is never a whit the less poisonous because it is gilded over with gold; nor a wolf is never a whit the less a wolf because he has put on a sheep's skin; nor the devil is never a whit the less a devil because he appears sometimes like an angel of light. So neither is sin any whit the less filthy and abominable by its being painted over with virtue's colors. The most dangerous vermin is too often to be found under the fairest and sweetest flowers; the fairest glove is often drawn over the foulest hand; and the richest robes are often put upon the filthiest bodies. So are the fairest and sweetest names upon the greatest and the most horrible vices and errors that be in the world.