For the Lord, i.e. for the service of the Lord, to assist you therein, in the servile and troublesome parts of it.
Related Commentaries of Numbers 18:6
Numbers 18:6
6 And I, behold, I have taken your brethren the Levites from among the children of Israel: to you they are given as a gift for the LORD, to do the service of the tabernacle of the congregation.