Commentary for Numbers 34:18

לִנְחֹל 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).

And one leader. The meaning of Scripture is that there is no obligation to make a real leader for every matter; the obligation to make a leader is only to be able to parcel out the land. Scripture mentioned them according to the greatness of the people in their own worth and not according to the importance of the tribes.