A.B. Simpson emphasizes the vital role of those who 'tarry by the stuff' in the mission of God, paralleling David's decision to share the spoils of victory with those who stayed behind to protect the vulnerable. He argues that both the front-line workers and the home supporters are equally important in the mission field, and that God calls some to remain and support the cause through prayer, resources, and encouragement. Simpson encourages believers to embrace the missionary idea, propagate it, and actively participate in sustaining those who go abroad. He highlights the power of prayer and the necessity of home missionaries, asserting that every Christian has a role in the Great Commission, whether at home or abroad. Ultimately, he calls for a collective effort to evangelize the world, reminding that all contributions, big or small, are significant in God's eyes.