Ezra the priest came twelve or thirteen years before Nehemiah to Jerusalem; and either tarried there, or went back to Babylon, being forced to do so by the king's command, or indispensable occasions, and then returned again with Nehemiah. All that could hear with understanding, i.e. and such children as were come to years of understanding.
Related Commentaries of Nehemiah 8:2
Nehemiah 8:2
2 And Ezra the priest brought the law before the congregation both of men and women, and all that could hear with understanding, upon the first day of the seventh month.