Thomas Brooks emphasizes the necessity of heartfelt obedience to Christ, asserting that true Christian obedience must come from the heart to be acceptable to God. He contrasts the genuine devotion of believers with the empty rituals of the Pharisees, who performed outwardly but lacked sincerity within. Brooks reminds us that God desires our hearts and will not accept mere external actions devoid of integrity. The heart, being the true seat of affection, must be engaged in our service to God, as He values what flows from a sincere heart. Ultimately, we must not offer God the shell of obedience while giving the devil the kernel of our true devotion.