A.W. Tozer discusses the three classes of man as described in 1 Corinthians: the natural man, the carnal man, and the spiritual man. He emphasizes that the natural man is unregenerate and cannot comprehend spiritual truths, while the carnal man, though saved, remains immature and influenced by his lower nature. The spiritual man, in contrast, is mature and led by the Holy Spirit, embodying the deeper spiritual life that God desires for His people. Tozer warns against the dangers of spiritual stagnation, urging believers to move beyond mere salvation and into a vibrant, active faith that fully embraces God's promises. He uses the example of Israel's journey from Egypt to Canaan to illustrate the importance of progressing in one's spiritual life.