A.B. Simpson emphasizes the importance of trusting God not only for spiritual salvation but also for physical healing and daily needs. He argues that true faith must be practical and applicable to our present circumstances, allowing us to experience God's divine power in our lives. Simpson challenges believers to recognize God as the ultimate source of healing and provision, urging them to transform their trials into blessings through faith. He highlights the significance of understanding Jehovah-rophi, the Lord who heals, and encourages a deeper reliance on God in all aspects of life.