Chuck Smith emphasizes the source of strength found in the joy of the Lord as demonstrated by the people of Israel during the reading of the Law by Ezra. He highlights their worship, which arose from recognizing God's grace and faithfulness, and the importance of understanding the Word of God for spiritual growth. The unity and determination of the people in rebuilding the wall serve as a testament to their faith and dedication, culminating in the realization that true strength comes from the joy that stems from hope in God. Smith encourages believers to find their strength in the joy of the Lord, which is rooted in His promises and presence.