Rashi on Numbers 34:18/רש"י על במדבר ל״ד:י״ח

1לִנְחֹל את הארץ [YE SHALL TAKE ONE PRINCE OF EVERY TRIBE], TO TAKE POSSESSION OF THE LAND i.e. that he should take possession and apportion it in your place (i.e. as your representatives; cf. Rashi on previous verse).