A.B. Simpson emphasizes the importance of trusting God and refraining from presumptuous actions that can lead to negative consequences, as illustrated by the tragic incident involving the ark of God. He encourages believers to rest in the Lord and wait patiently, reminding them that God's timing and methods are superior to human efforts. Simpson highlights that true faith often involves letting go and allowing God to work in His own way, rather than striving restlessly to control situations. The sermon reassures that even when circumstances appear dire, God is aware and will act at the right moment if we fully trust Him.