2 Chronicles 23:4
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; 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;
Jehoiada ordered that a third part of the priests and Levites entering on Sabbath duty should serve as porters and guards of the doors and entrances of the temple. The arrangement was made for restoring Joash to the throne, dividing those coming on duty into assigned groups for his protection. That organized guarding enabled Joash to be proclaimed king and brought Athaliah's corrupt rule to an end.
The order belongs to the revolt against Athaliah to restore Joash, the child heir hidden in the temple for six years. The revolt ended with Athaliah's death and Joash enthroned at seven years old, and he did right while Jehoiada the high priest counseled him. The coronation it describes is the same event surrounding King Joash's coronation described in 2 Kings 11. This former arrangement for organizing temple service was later used as a precedent for Hezekiah's assignment of the Levites to their service when he reopened the temple.
The Sabbath it mentions is the weekly Sabbath, the Sabbath of the Lord, rather than a festival Sabbath or a sabbath of the land. Its incidental assignment of Sabbath duty at Jehoash's accession shows that Sabbath observance remained embedded in the temple's organized service and in the religious life of the people.