It was eaten by the people of Israel who had returned from exile, and also by every one who had joined them and separated himself from the uncleanness of the peoples of the land to worship the LORD, the God of Israel.
Here we have, I. The Jews' enemies made their friends. When they received this order from the king they came with as much haste to encourage and assist the work as their predecessors had done to put a stop to it, Ezr 4:23. What the king ordered they did, and, because they would not be thought to do it with reluctance, they did it speedily, Ezr 6:13.
Commenting on Ezra 6:13-22
AND OF THE PASSOVER. (Ezr 6:19-22) all such as had separated themselves . . . from the filthiness of the heathen of the land--that is, who had given satisfactory evidence of being true proselytes by not only renouncing the impure worship of idolatry, but by undergoing the rite of circumcision, a condition indispensable to a participation of the passover.
And the children of Israel, which were come again out of captivity, and all such as had separated themselves unto them from the filthiness of the heathen of the land, to seek the LORD God of Israel, did eat, (i) Who were of the heathen and forsook their idolatry to worship the true God.