Matthew Poole and continuators on Numbers 4:3

3 From thirty years old and upward, even until fifty years old , all that enter into the host , to do the work of the tabernacle of the congregation.

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 Iohn and Christ entred not upon their Ministery till that age. And it may still seem to be the fittest season for mens undertaking the Ministery of the Gospel, except in case of extraordinary abilities or the Churches pressing necessity. Object. They might enter upon this work at their 25th. year, Numb. 8. 24. and in David's time and afterward at their twentieth year. Answ. 1. Their first entrance upon their work was at their five and twentieth year, when they began as learners and acted onely under the inspection and direction of their brethren, but in their thirtieth year they were compleatly 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.

When they were exempted from the toilsome work of carrying burdens, but not discharged from the honourable and easie work done within the Tabernacle, Numb. 8. 26.

(i. e.) That do and may enter, having no defect, Levit. 21. 17. nor other impediment.

The society of sacred Ministers he calls an host, because of that excellent order which was among them as to persons, place, time, the matter and manner, of their services.