Thomas Brooks emphasizes the necessity of mortifying sin to achieve true holiness, asserting that beloved sins act as poison to the soul, hindering spiritual growth. He encourages believers to actively dethrone their 'darling sins' through the power of the Spirit, comparing the process to the need for a poisoned person to vomit out the toxin. Brooks highlights five meditations that can aid in this process, ultimately concluding that the most effective means is to focus on the death and sufferings of Christ, which empowers believers to overcome their besetting sins. He urges the congregation to continually look to a crucified Christ for strength in their battle against sin.

Thomas Brooks emphasizes that true mortification of sin can only be achieved through faith in Christ's sacrifice, rather than relying on personal resolutions or efforts. He highlights the struggle of believers who, despite their attempts to combat sin, find themselves overwhelmed and unable to restore their communion with God. Brooks urges Christians to exercise their faith and draw strength from Christ, as it is through this divine connection that the burden of sin can be lifted. He laments that many believers fail to recognize the importance of looking to a crucified Christ for healing and victory over sin. Ultimately, he asserts that a deeper faith in Christ will lead to a greater ability to overcome sin.

Thomas Brooks emphasizes the necessity of mortifying our 'darling sins' rather than merely hiding them. He argues that overcoming a single significant sin brings far greater joy and peace than the fleeting pleasures of sinning. The true joy that comes from conquering sin is pure, lasting, and noble, contrasting sharply with the corrupt and diminishing joy of indulging in sin. Brooks warns that those who choose to dally with sin will face separation from God and the consequences of their actions, ultimately leading to torment. He urges Christians to actively seek victory over their most cherished sins to experience a life filled with divine joy and peace.

Thomas Brooks emphasizes the necessity of relying on the grace of the Spirit to overcome sin, arguing that mere resolutions are insufficient to conquer lust. He illustrates the destructive potential of even one unmortified lust, comparing it to various biblical examples of singular failures leading to great calamities. Brooks urges believers to actively pursue the mortification of every lust, as neglecting even one can lead to spiritual turmoil. He highlights that true cleansing comes only through the blood of Christ and the power of the Spirit, not through human efforts or rituals. The sermon calls for a serious commitment to eradicate sin from one's life to maintain spiritual peace.