By divine direction the tribe of Levi was set apart for the service of the sanctuary. In the earliest times every man was the priest of his own household. In the days of Abraham the priesthood was regarded as the birthright of the eldest son. Now, instead of the first-born of all Israel, the Lord accepted the tribe of Levi for the work of the sanctuary. By this signal honor He manifested His approval of their fidelity, both in adhering to His service and in executing His judgments when Israel apostatized in the worship of the golden calf. The priesthood, however, was restricted to the family of Aaron. Aaron and his sons alone were permitted to minister before the Lord; the rest of the tribe were entrusted with the charge of the tabernacle and its furniture, and they were to attend upon the priests in their ministration, but they were not to sacrifice, to burn incense, or to see the holy things till they were covered.

Efter Guds anvisning blev Levis stamme sat til side til at varetage tjenesten i helligdommen. I de ældste tider var hver mand sin families præst. På Abrahams tid blev præsteembedet betragtet som den ældste søns førstefødselsret. Nu antog Herren Levis stamme til arbejdet i helligdommen i stedet for de førstefødte fra hele Israel. Ved denne særskilte hæder viste han sin anerkendelse af den troskab, de havde lagt for dagen, både ved at vedblive at tjene ham og ved at fuldbyrde hans domme, da Israel svigtede Gud og tilbad guldkalven. Præsteembedet var imidlertid forbeholdt Arons familie. Aron og hans sønner var de eneste, der fik lov til at gøre tjeneste for Herren. De øvrige af stammen fik betroet pasningen af tabernaklet og dets tilbehør, og de skulle hjælpe præsterne i deres tjeneste; men de skulle ikke ofre og brænde røgelse og måtte ikke se de hellige ting, før de var dækket til.