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 gatekeepers 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 was performing 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 was performing 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.