'Duty' in the Bible

Now in accordance with the ordinance of his father David, he appointed the divisions of the priests for their service, and the Levites for their duties of praise and ministering and serving before the priests as every day required, and the gatekeepers by their divisions at every gate; for David the man of God had so commanded.

So the Levites and all Judah acted in accordance with everything that Jehoiada the priest had commanded; and every man took his men who were to resume duty on the Sabbath, with those who were to go off duty on the Sabbath, for Jehoiada the priest did not dismiss [any of] the divisions [from their duties].

Then the men who were designated by name rose up and took the captives, and from the spoil they clothed all those who were naked; they clothed them and gave them sandals, and fed them and gave them [something to] drink, anointed them [with oil, as was a host’s duty], and led all the feeble ones on donkeys, and they brought them to Jericho, the City of Palm Trees, to their brothers (fellow descendants of Israel, i.e. Jacob). Then they returned to Samaria.

without regard to their genealogical registration, to the males from thirty years old and upward—everyone who entered the house of the Lord for his daily obligations—for their service in accordance with their duties by their divisions;