Num Numbers, chapter Book of Numbers, chapter 1
But the Levi'im shall encamp around the Mishkan HaEdut, that there be no ketzef (wrath) fall upon the Adat Bnei Yisroel; and the Levi'im shall be shomer mishmeret (watch the watch, attend to, keep the charge, the reverence) of the Mishkan HaEdut.