2 Chronicles 23:4

This is the thing that ye 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

And 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

And 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

And 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

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

Luke 1:8-9

But it came to pass during his service as a priest in the course of his division in the presence of God,

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
And 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
And 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
But it came to pass during his service as a priest in the course of his division in the presence of God,

Porters

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