The book of Joshua is a very positive book in the Bible. It’s 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. It is also a book about our responsibility towards 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 his church, and what response the Lord is calling from his church. For Joshua 8, there are a number of details that clearly testify to God’s faithfulness. You can begin your sermon by focusing on the battle of Ai and then move on to the covenant renewal ceremony. When explaining the response which we must make, it might be a good idea to focus on covenant renewal.
1 And the LORD said to Joshua, “Do not fear and do not be dismayed. Take all the fighting men with you, and arise, go up to Ai. See, I have given into your hand the king of Ai, and his people, his city, and his land.