At this point Ezra features for the first time in the book. He had originally come to Jerusalem in 458 BC, and Nehemiah had joined him about 13 years later in 445 BC.
Understanding is key to worship, for God has given us minds which are capable of appreciating his truth and responding to it. We are to worship the Lord with all our heart, soul, mind and strength. True religion does not hide or obscure the truth, but makes it as clear as possible. True worship does not involve switching off the mind or deadening it by mindless repetition, but it furnishes the mind with exalted truths that fill us with appreciation for the greatness of our God.