וְשֵׁרֵ֨ת אֶת־אֶחָ֜יו בְּאֹ֤הֶל מוֹעֵד֙ לִשְׁמֹ֣ר מִשְׁמֶ֔רֶת וַעֲבֹדָ֖ה לֹ֣א יַעֲבֹ֑ד כָּ֛כָה תַּעֲשֶׂ֥ה לַלְוִיִּ֖ם בְּמִשְׁמְרֹתָֽם׃ (פ)
그 형제와 함께 회막에서 모시는 직무를 지킬 것이요 일하지 아니할 것이라 너는 레위인의 직무에 대하여 이같이 할지니라
Rashi on Numbers
לשמר משמרת TO KEEP THE CHARGE — i.e. to encamp round about the tent of meeting in order to keep strangers away, and to erect and dismantle it at the time of finishing and beginning the journey.
Rashbam on Numbers
(1) THEY MAY ASSIST/SERVE -- both groups -- THEIR BROTHER LEVITES ... BY STANDING GUARD, BUT THEY SHALL PERFORM NO LABOR.
Chizkuni
ושרת את אחיו, “but shall minister with their brethren;” when this Levite turns fifty, he shall minister with the other Levites who have already turned fifty. This is based on Numbers 1,50: “they are to encamp immediately around the Tabernacle.”