He commanded them, saying, This is the thing that you shall do: a third part of you, who come in on the Shabbat, shall be keepers of the watch of the king's house;
This was the ordering of them in their service, to come into the house of the LORD according to the ordinance [given] to them by Aharon their father, as the LORD, the God of Yisra'el, had commanded him.
This is the thing that you shall do: a third part of you, who come in on the Shabbat, of the Kohanim and of the Levites, shall be porters of the thresholds;
So the Levites and all Yehudah did according to all that Yehoiada the Kohen commanded: and they took every man his men, those who were to come in on the Shabbat; with those who were to go out on the Shabbat; for Yehoiada the Kohen didn't dismiss the shift.