Commentary for Numbers 34:17

אשר ינחלו לכם [THESE ARE THE … MEN] WHO SHALL TAKE POSSESSION OF THE LAND לכם — i.e., for you. Each prince was the agent of his tribe and divided the inheritance of the tribe amongst the families and again amongst the men, selecting for each a portion fitting for him. What they did was done (was legal) just as if they (the tribes) had appointed them their representatives (Kiddushin 42b). — It would not be right to explain this לכם as all other לכם (“to you”) which occur in the Bible, for if so it should have written יַנְחִילוּ לכם (Hiphil), “they will give the possession to you”. But יִנְחֲלוּ (Kal), implies that they themselves take possession לכם, “for you” and in your place. It is the same as, (Exodus 14:14): “The Lord will fight לכם” — “for you”.

For your sake. The word ינחלו ["shall inherit"] implies that they would inherit it themselves ["i.e., on their own"], while לכם ["for you"] implies that they would cause you to inherit it. Therefore, Rashi explains, “Who shall inherit for your sake.”