Numbers 4:3

From thirty years old: this age was prescribed, as the age of full strength of body, and therefore most proper for their present laborious work of carrying the parts and vessels of the tabernacle; and of maturity of judgment, which is necessary for the right management of holy services; whence even John and Christ entered not upon their ministry till that age. And it may still seem to be the fittest season for men's undertaking the ministry of the gospel, except in case of extraordinary abilities, or the church's pressing necessity. Object. They might enter upon this work at their twenty-fifth year, Numbers 8:24, and in David's time and afterward at their twentieth year. Answ.

1. Their first entrance upon their work was at their twenty-fifth year, when they began as learners, and acted only under the inspection and direction of their brethren; but in their thirtieth year they were completely admitted to a full discharge of their whole office.

2. David, being a prophet, and particularly directed by God in the affairs of the temple, might and did make a change in this matter, which he might the better do, both because it was but a change in a circumstance, and because the magnificence of the temple, and the great multitude of sacred utensils and sacrifices, required a greater number of attendants than formerly was necessary. Until fifty years old, when they were exempted from the toilsome work of carrying burdens, but not discharged from the honourable and easy work done within the tabernacle, Numbers 8:26. All that enter, i.e. that do and may enter, having no defect, Leviticus 21:17, nor other impediment. The society of sacred ministers he calls a host, because of that excellent order which was among them, as to persons, place, time, the matter and manner of their services.