Ezra 6:20-21

20All of the priests and Levites were ceremonially clean, because they had purified themselves. They killed the Passover lamb for themselves, their priestly brothers, and all the exiles.

21The Israelites who had returned from exile ate it, together with all who had separated themselves from the uncleanness of the Gentiles of the land in order to worship the Lord, the God of Israel.