Sforno on Numbers
נתונים נתונים המה לו, all their (the Levites’) service was to be performed at the instruction of Aaron, to whom the Levites had been delegated by the people.
Rashbam on Numbers
נתונים,נתונים, the repetition of the word is similar to the repetition נתן תתן להם אחזת נחלה, “be sure to give” in English, in Numbers 27,7.