George Fox warns believers to speak plainly and truthfully, allowing their words to reflect the light of Christ within them. He emphasizes that words should be life-giving and rooted in the grace of God, contrasting this with the consequences of ungodliness and deceit. Fox encourages the faithful to dwell in the light, which leads to purity in speech and unity among believers, ultimately producing righteousness. He reminds them that true ministry and prophecy come not from human will but from God, urging them to abide in Christ as branches of the true vine. The sermon calls for a life of integrity and sincerity, free from hypocrisy and flattery.