2 Chronicles 23:4

This is the thing that you shall do. A third part of you, who come in on the Sabbath, of the priests and of the Levites, shall be porters of the thresholds.

1 Chronicles 9:25

Their brothers, in their villages, were to come in every seven days from time to time to be with them:

1 Chronicles 23:3-6

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

1 Chronicles 24:3-6

David with Zadok of the sons of Eleazar, and Ahimelech of the sons of Ithamar, divided them according to their ordering in their service.

1 Chronicles 26:13-16

They cast lots, the small as well as the great, according to their fathers' houses, for every gate.

Luke 1:8-9

Now it happened, while he executed the priest's office before God in the order of his division,

Treasury of Scripture Knowledge

Summary

This is the thing that ye shall do; A third part of you entering on the sabbath, of the priests and of the Levites, shall be porters of the doors;

Bible References

Entering

1 Chronicles 23:3
The Levites were numbered from thirty years old and upward: and their number by their polls, man by man, was thirty-eight thousand.
1 Chronicles 24:3
David with Zadok of the sons of Eleazar, and Ahimelech of the sons of Ithamar, divided them according to their ordering in their service.
Luke 1:8
Now it happened, while he executed the priest's office before God in the order of his division,

Porters

1 Chronicles 26:13
They cast lots, the small as well as the great, according to their fathers' houses, for every gate.