NUM 3:38

38 And those that encamp in front of the Mishkan toward the east, even in front of the Ohel Mo'ed eastward, shall be Moshe, and Aharon and his banim, shomrim mishmeret HaMikdash [(standing guard duty over the holy area)] on behalf of the Bnei Yisroel; and the zar that shall encroach shall be put to death.