The Kohathites were entrusted with the care of the holy furniture when it was on the move
upon God’s instruction, whereas Moses, Aaron, and his sons were entrusted with that responsibility when the tabernacle was stationary. The sons of Aaron would serve specifically to protect the people of Israel
(ESV), or more accurately, to meet the needs of the sons of Israel
(Numbers 3:38).
38 Moïse, Aaron et ses fils campaient devant le tabernacle, à l'orient, devant la tente d'assignation, au levant; ils avaient la garde et le soin du sanctuaire, remis à la garde des enfants d'Israël; et l'étranger qui s'approchera sera puni de mort.