1 Chronicles 23:27

So among the last acts of David was the numbering of the sons of Levi, from twenty years old and over.

1 Chronicles 23:24

These were the sons of Levi, grouped by families, the heads of the families of those who were numbered by name, by heads, all those of twenty years old and over who did the work of the house of the Lord.

2 Samuel 23:1

Now these are the last words of David. David, the son of Jesse, says, the man who was lifted up on high, the man on whom the God of Jacob put the holy oil, the loved one of Israel's songs, says:

1 Chronicles 23:3

And the Levites, all those of thirty years old and over, were numbered; and the number of them, by heads, man by man, was thirty-eight thousand.

Psalm 72:20

The prayers of David, the son of Jesse, are ended.

Treasury of Scripture Knowledge

Summary

For by the last words of David the Levites were numbered from twenty years old and above:

General references

Bible References

By the last

1 Chronicles 23:3
And the Levites, all those of thirty years old and over, were numbered; and the number of them, by heads, man by man, was thirty-eight thousand.
2 Samuel 23:1
Now these are the last words of David. David, the son of Jesse, says, the man who was lifted up on high, the man on whom the God of Jacob put the holy oil, the loved one of Israel's songs, says:
Psalm 72:20
The prayers of David, the son of Jesse, are ended.

General references

Numbers 4:35
Numbering all those from thirty to fifty years old who were able to do the work in the Tent of meeting;

Basic English, produced by Mr C. K. Ogden of the Orthological Institute - public domain