A.B. Simpson emphasizes the necessity of receiving power from the Holy Spirit to fulfill the Great Commission, highlighting that human beings are inherently weak and in need of divine strength. He explains that this power is not merely an abstract force but the presence of the Holy Spirit, which enables believers to witness effectively and live transformed lives. Simpson illustrates how the early church exemplified this power through their character, love, and commitment to spreading the gospel, demonstrating that true power comes from obedience to God's will. He also discusses the importance of the Holy Spirit in guiding the church, providing supernatural gifts, and empowering believers to endure suffering for Christ's sake. Ultimately, he calls for a renewed baptism of the Holy Spirit to empower the church for effective service in these challenging times.