פירוש על דברי הימים ב 23:4

of those coming in on the Sabbath And also those leaving on the Sabbath, as is written below (verse 8): “and each one took his men, those coming in on the Sabbath with those leaving on the Sabbath.” The watches were renewed on the Sabbath (See Taanith 2:6,7), viz. the priests and the Levites; one [watch] would leave and one would come in. Jehoiada detained the watch that was leaving with the watch that was coming in, and divided them into three divisions.