Here "the name of Yahweh" stands for Yahweh himself and his authority. Alternate translation: "to be his special servants" or "to serve as a representative of Yahweh" (See: [[rc://en/ta/man/translate/figs-metonymy]])
Here "him" represents all the Levites. Alternate translation: "the Levites and their descendants forever" (See: [[rc://en/ta/man/translate/figs-synecdoche]])