Thomas Brooks emphasizes the dangers of hypocrisy in religious practice, illustrating how the Pharisees performed many outward acts of piety without true inward transformation. He argues that a hypocrite may engage in prayer, fasting, and giving, yet lacks the genuine heart and spiritual principles that should underlie these actions. Brooks warns that such hollow practices, devoid of sincere love and faith, ultimately lead to spiritual ruin. He contrasts the hypocrite with a sincere Christian, who finds true fulfillment in Christ rather than mere religious duties. The sermon serves as a call to examine the heart's condition in relation to God and the authenticity of one's faith.

("Touchstone of Sincerity") "The Pharisee took his stand and was praying like this: God, I thank You that I’m not like other people—greedy, unrighteous, adulterers, or even like this tax collector. I fast twice a week; I give a tenth of everything I get." Luke 18:11-12 A hypocrite . . . may know much, and pray much, and hear much, and fast much, and give much, and obey much —and all to no purpose, because he never does anything in a right manner; he never carries on his work from inward principles of faith, fervency, love, delight, etc. The scribes and pharisees fasted, prayed and gave alms—but their hearts were not changed, renewed, nor sanctified—and this proved their eternal bane. A hypocrite never performs religious duties from spiritual principles, nor in a spiritual manner. A hypocrite is never inclined, moved, and carried to God, to Christ, to holy duties—by the power of a new and inward principle of grace working a suitableness between his heart and the things of God. A hypocrite rests satisfied in the mere external acts of religion, though he never feels anything of the power of religion in his own soul. A hypocrite looks to his words in prayer, and to his voice in prayer, and to his gestures in prayer—but he never looks to the frame of his heart in prayer. A hypocrite's heart is never touched with the words his tongue utters; a hypocrite's soul is never divinely affected, delighted, or graciously warmed with any duty he performs. A hypocrite's spiritual performances never flow from spiritual principles, nor from a sanctified heart. Though his works may be new, yet his heart remains old; his new practices always spring from old principles; and this will prove the hypocrite's bane, as you may see in Isaiah 1:15, "When you make many prayers, I will not hear, for your hands are full of blood." These were unsanctified ones; their practices were new—but their hearts were old still. A hypocrite has no . . . inward, saving, transforming, experimental, affectionate, practical knowledge of God. A sincere Christian is enamored with Christ above all. He cannot be satisfied nor contented with duties or ordinances, without enjoying Christ in them, who is the life, soul, and substance of them. But when hypocrites do duties—all they do is from common principles, from natural principles, and from an unsanctified heart—and that mars all. Hypocrites make a great profession and are much in the outward actions of religion; they make a very fair show, they hear, they read, they pray, they fast, they sing psalms, and they give alms; but these duties being not performed from a principle of divine love, nor from a principle of spiritual life, nor from a sanctified frame of heart—are all lost, and the authors of them are undone forever and ever. "If anyone does not love the Lord, that person is cursed!" 1 Cor. 16:22