Num 1:53

וְהַלְוִיִּ֞ם יַחֲנ֤וּ סָבִיב֙ לְמִשְׁכַּ֣ן הָעֵדֻ֔ת וְלֹֽא־יִהְיֶ֣ה קֶ֔צֶף עַל־עֲדַ֖ת בְּנֵ֣י יִשְׂרָאֵ֑ל וְשָׁמְרוּ֙ הַלְוִיִּ֔ם אֶת־מִשְׁמֶ֖רֶת מִשְׁכַּ֥ן הָעֵדֽוּת׃

But the Levites are to camp around the tabernacle of the Testimony and watch over it, so that no wrath will fall on the congregation of Israel. So the Levites are responsible for the tabernacle of the Testimony.”