Because they now knew God's mind, and their own duty, which they were resolved to practise; which gave them ground of hope and trust in God's mercy, and consequently of great and just joy.
Related Commentaries of Nehemiah 8:12
Nehemiah 8:12
12 And all the people went their way to eat, and to drink, and to send portions, and to make great mirth, because they had understood the words that were declared unto them.