Nehemiah 13:22; Nehemiah 13:30

22 Then I commanded the Levites that they should purify themselves and come and guard the gates, to keep the Sabbath day holy. Remember this also in my favor, O my God, and spare me according to the greatness of your steadfast love.

30 Thus I cleansed them from everything foreign, and I established the duties of the priests and Levites, each in his work;