Ezra 6:18-20

Amplified Bible

¹⁸ Then they appointed the priests to their divisions and the Levites in their orders for the service of God at Jerusalem, as it is written in the book of Moses.

The Passover Observed

¹⁹ The [former] exiles kept the Passover on the fourteenth [day] of the first month. ²⁰ For the priests and the Levites had purified themselves together; all of them were [ceremonially] clean. So they slaughtered the Passover lamb for all the exiles, for their brothers the priests, and for themselves.