Ezra 6:20-21

20For the priests and the Levites had purified themselves together; all of them were clean. So they slaughtered the Passover lamb for all the returned exiles, for their fellow priests, and for themselves.

21It 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.