Num Numbers, chapter Book of Numbers, chapter 3
And they3:7 the Levi'im shall be shomer mishmeret (watch the watch, keep the guard duty) for him and for the mishmeret kol HaEdah (duty of the whole Congregation) before the Ohel Mo'ed, to do avodat HaMishkan (the work, service of the Mishkan).
And they shall be shomer mishmeret over kol klei Ohel Mo'ed (all the vessels, furnishings of the Ohel Mo'ed) for the Bnei Yisroel, doing the avodat HaMishkan (work of the Mishkan). Lev 8:35And thou shalt give the Levi'im unto Aharon and to his banim; they are wholly given unto him from among the Bnei Yisroel. Num 8:19