The book of Joshua is a very positive book in the Bible. It is a book about the faithfulness of God, written to strengthen our faith in his promises, particularly the promise that Jesus Christ is preparing a new home for us where we can enjoy rest in his presence (Hebrews 4:1–16). It is also a book about our responsibility toward God. The Lord has made promises to us. He has shown himself to be worthy of our trust. And in this book we will see how the Lord calls us to now be faithful to him.
In light of the purpose of Joshua, the goal of your sermon must be to show how God has been faithful to us, and what response the Lord is calling us to. The final three verses of Joshua 21 especially encourage us to stop and reflect in depth upon God’s faithfulness. Your sermon should show how this faithfulness was seen in God’s actions to bring his people into the land as well as in the work of Jesus Christ. Explaining the different levels of promise fulfillment will also help Christians not to become confused with the modern state of Israel. Ultimately you want to encourage God’s church to live in the light of God’s promises knowing that God always does what he says.
43 Thus the LORD gave to Israel all the land that he swore to give to their fathers. And they took possession of it, and they settled there.