'Duty' in the Bible

Two units of you, all those who go out [off duty] on the Sabbath, shall also keep watch over the house (temple) of the Lord for [the protection of] the king.

The captains of hundreds acted in accordance with everything that Jehoiada the priest commanded; and each of them took his men who were to come in (on duty) on the Sabbath, with those who were to go out (off duty) on the Sabbath, and they came to Jehoiada the priest.