Divrey Hayamim Alef 23:31-32

Orthodox Jewish Bible

³¹ And to offer all olot (burnt offerings) unto Hashem on Shabbatot, at Rosh Chodesh, and at mo’adim, according to their number ordained for them, tamid before Hashem;

³² And that they should be shomer to keep the mishmeret (watch, guard responsibility) of the Ohel Mo’ed and the mishmeret of the Kodesh, and the mishmeret of the Bnei Aharon their brethren, in the avodas Beis Hashem.