American Standard Version (ASV):
This is the thing that ye shall do: a third part of you, that come in on the sabbath, of the priests and of the Levites, shall be porters of the thresholds;
King James Version (KJV):
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;