Numbers 4:2-3

Take the sum of the sons of Kohath from among the sons of Levi, after their families, by the house of their fathers,

Sons of Kohath ... from thirty years old and upward. This age was specifically fixed on (see the note at Numbers 8:24) as the full maturity of bodily energy to perform the laborious duties assigned them in the wilderness, as well as of mental activity to assist in the management of the sacred services. And hence, it was the period of life at which the Baptist and Christ entered on their respective ministries.

Even until fifty. The term prescribed for active duty was a period of twenty years, at the end of which they were exempted from the physical labours of the office, though still expected to attend in the tabernacle (Numbers 8:26).

All that enter into the host - so called from their number, the order and discipline maintained through their ranks, and them special duty as guards of the tabernacle. х Tsaabaa' (H6635), rendered host, however, signifies also a station or office; and hence, the passage may be rendered, 'All that enter into the sacerdotal office' (Numbers 4:23.)]