Charles Ellicott Commentary Ezra 6:22

"and kept the feast of unleavened bread seven days with joy: for Jehovah had made them joyful, and had turned the heart of the king of Assyria unto them, to strengthen their hands in the work of the house of God, the God of Israel." — Ezra 6:22 (ASV)

And kept the feast. —The Mazzoth, or week of unleavened bread, was the symbol of entire separation from evil, to the service of that God whom on the Passover they accepted as their God. The special joy of this feast was the feeling that the Lord had “turned the heart of the king of Assyria.” The king of Persia is so called as a reminder of their oppression by his forerunners.