A.B. Simpson emphasizes the importance of motives in our service to God, illustrating that our redemption, salvation, calling, sanctification, and the endowment of the Holy Spirit all bind us to a life of service. He argues that our Christian experiences and character development are not just for our benefit but are meant to help others, and that true joy comes from living a life of usefulness. Simpson encourages believers to recognize the preciousness of souls and the opportunities for service that God provides, urging them to respond to these calls with dedication and love. Ultimately, he reminds us that the love of Christ is the strongest motivation to serve, compelling us to offer our lives as living sacrifices on His altar.