Numbers 10:10-11

¹⁰If any time ye shall have a feast, and holidays, and calends, that is, the first day of the month, ye shall sing in trumps upon the burnt sacrifices, and the peaceable sacrifices, that those or they be to you into remembering of your God; I am your Lord God.

¹¹In the second year, in the second month, in the twentieth day of the month, the cloud was raised up from the tabernacle of the bond of peace.