'Necessary' in the Bible

And they will have the care of all the vessels of the Tent of meeting, and will do for the children of Israel all the necessary work of the House.

And the hangings for the open space round the House and the altar, and the curtain for its doorway, with the cords and all the things used for them; whatever is necessary for these, they are to do.

And this is the law for him who is separate, when the necessary days are ended: he is to come to the door of the Tent of meeting,

Only the Levites shall perform the service of the Tent of Meeting (tabernacle), and they shall bear their iniquity; it shall be a statute forever throughout your generations, that the Levites shall have no inheritance [of land] among the children of Israel.