Joshua gives a summary of the history of Israel, emphasizing God’s faithfulness toward the people and their forefathers. He then asks if they intend to live as God has told them to do. They strongly agree to follow God.
Remembering God’s faithfulness to us and committing to following Him is what ceremonies like baptism and communion are about. We are reminded of what God has done and we should respond with grateful commitments to honor Him with our lives.