TSK · Numbers 4:23

from thirty years old and upward even until fifty years old, all who enter into the service, to do the work in the Tent of Meeting.

The Levites were numbered from thirty years old and upward: and their number by their polls, man by man, was thirty-eight thousand.

For by the last words of David the sons of Levi were numbered, from twenty years old and upward.

For we know that the law is spiritual, but I am fleshly, sold under sin.

in the word of truth, in the power of God; by the armor of righteousness on the right hand and on the left,

For the flesh lusts against the Spirit, and the Spirit against the flesh; and these are contrary to one another, that you may not do the things that you desire.

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

You therefore must endure hardship, as a good soldier of Christ Jesus.