The sermon emphasizes the unwavering faithfulness of God, highlighting His promises as the cornerstone of His relationship with His people, drawing heavily from the book of Joshua. It asserts that God's promises are not contingent on human effort but are fulfilled through His own sovereign action, exemplified by the granting of land, rest, and victory over enemies. The message underscores that true faith rests in God's doing, not human striving, and points to the ultimate fulfillment of these promises in Christ, offering a future rest and complete salvation for those who believe, echoing the assurance that God's promises are true and will be fully realized.