A.W. Tozer emphasizes that new Christians must quickly learn that Jesus Christ is all they need for their spiritual journey. He asserts that true belief in Christ allows individuals to declare their independence from external validations and reassurances. Tozer critiques modern evangelicalism for its lack of assurance and tendency to seek external evidence to support faith, which can lead to doubt when faced with opposing views from science and philosophy. He encourages believers to turn to the Scriptures, particularly the books of John, Ephesians, Colossians, and Hebrews, to find the assurance they seek in Christ alone.

Thomas Brooks emphasizes that a suffering Christ is the ultimate source of fulfillment and satisfaction for Christians, encapsulating all the perfections and needs of humanity. He illustrates that Christ embodies everything believers require—nourishment, protection, guidance, and healing—making Him indispensable for both spiritual and temporal needs. Brooks argues that the worth of Christ surpasses all earthly treasures, and in Him, believers find complete satisfaction and joy. He challenges Christians to recognize the sufficiency of Christ in their lives, highlighting that nothing more is needed for holiness and happiness.

A.W. Tozer emphasizes the sufficiency of Christ in his sermon 'Walking in the Light of His Presence', criticizing the tendency to seek validation of Christ through psychology, philosophy, and science. He points out the absurdity of modern believers seeking approval from worldly figures, while the New Testament clearly states that God commands repentance through Christ, who has been validated by His resurrection. Tozer asserts that Christ does not need external validation; He is self-validating as the Second person of the Godhead, and every individual ultimately stands before Him for judgment. The resurrection of Christ serves as the ultimate assurance of His identity and authority.