2 Chronicles 31:16
Beside their genealogy of males, from three years old and upward, even unto every one that entereth into the house of the LORD, his daily portion for their service in their charges according to their courses;
Ezra 3:4
They kept also the feast of tabernacles, as it is written, and offered the daily burnt offerings by number, according to the custom, as the duty of every day required;
Leviticus 21:22-23
He shall eat the bread of his God, both of the most holy, and of the holy.
1 Chronicles 23:3
Now the Levites were numbered from the age of thirty years and upward: and their number by their polls, man by man, was thirty and eight thousand.