Num 3:38

וְהַחֹנִ֣ים לִפְנֵ֣י הַמִּשְׁכָּ֡ן קֵ֣דְמָה לִפְנֵי֩ אֹֽהֶל־מוֹעֵ֨ד מִזְרָ֜חָה מֹשֶׁ֣ה וְאַהֲרֹ֣ן וּבָנָ֗יו שֹֽׁמְרִים֙ מִשְׁמֶ֣רֶת הַמִּקְדָּ֔שׁ לְמִשְׁמֶ֖רֶת בְּנֵ֣י יִשְׂרָאֵ֑ל וְהַזָּ֥ר הַקָּרֵ֖ב יוּמָֽת׃

Moses, Aaron, and Aaron’s sons were to camp to the east of the tabernacle, toward the sunrise, before the Tent of Meeting. They were to perform the duties of the sanctuary as a service on behalf of the Israelites; but any outsider who approached the sanctuary was to be put to death.