C. F. Keil and Franz Delitzsch on Numbers 4:49

Num 4:49

“According to the commandment of Jehovah, they appointed them through the hand of Moses (i.e., under his direction), each one to his service, and his burden, and his mustered things (פּקדיו), i.e., the things assigned to him at the time of the mustering as his special charge (see Exo 38:21). Spiritual Organization of the

Congregation of Israel - Numbers 5-6

From the outward organization of the tribes of Israel as the army of Jehovah, the law proceeds to their internal moral and spiritual order, for the purpose of giving an  inward support, both moral and religious, to their outward or social and political unity. This is the object of the directions concerning the removal of unclean persons from the camp (Num 5:1-4), the restitution of anything unjustly appropriated (Num 5:5-10), the course to be pursued with a wife suspected of adultery (Num 5:11-31), and also of the laws relating to the Nazarite (Num 6:1-21), and to the priestly blessing (Num 6:22-27).