TSK · Numbers 4:3

from twenty years old and upward, all that are able to go forth to war in Israel, thou and Aaron shall number them by their hosts.

And they shall keep his charge, and the charge of the whole congregation before the tent of meeting, to do the service of the tabernacle.

from thirty years old and upward even unto fifty years old shalt thou number them, every one that entereth upon the service, to do the work of the tent of meeting.

from thirty years old and upward even unto fifty years old, every one that entered in to do the work of service, and the work of bearing burdens in the tent of meeting,

[ seemeth it but] a small thing unto you, that the God of Israel hath separated you from the congregation of Israel, to bring you near to himself, to do the service of the tabernacle of Jehovah, and to stand before the congregation to minister unto them;

And their brethren the Levites were appointed for all the service of the tabernacle of the house of God.

These were the sons of Levi after their fathers' houses, even the heads of the fathers' [houses] of those of them that were counted, in the number of names by their polls, who did the work for the service of the house of Jehovah, from twenty years old and upward.

and the pattern of all that he had by the Spirit, for the courts of the house of Jehovah, and for all the chambers round about, for the treasuries of the house of God, and for the treasuries of the dedicated things;

and them that were reckoned by genealogy of the priests by their fathers' houses, and the Levites from twenty years old and upward, in their offices by their courses;

And Jesus himself, when he began [to teach], was about thirty years of age, being the son (as was supposed) of Joseph, the [son] of Heli,

Finally, be strong in the Lord, and in the strength of his might.

Faithful is the saying, If a man seeketh the office of a bishop, he desireth a good work.