Matthew Poole and continuators on Numbers 36:6

6 This is the thing which the LORD doth command concerning the daughters of Zelophehad, saying, Let them marry to whom they think best: only to the family of the tribe of their father shall they marry.

They seem hereby to be confined not only to the same Tribe, but also to the family of their Tribe, as appears from the reason of the Law, for God would have the inheritance of Families as well as Tribes kept intire and unmixed: and this was one reason of that Law of marrying the Brothers wife, Deut. 25. And although the next verse may seem to thwart this interpretation, the reason of this Law being there given that inheritances might not go from Tribe to Tribe, yet ver. 8. confirms it, where the very same phrase is repeated, and that more emphatically, that such shall marry one of the family of the Tribe of her Father; and this further reason and restriction is added, that they may enjoy every man the inheritance (not onely of his Tribe, but) of his Fathers, to wit, belonging to his fathers family.

Marginal references: Heb. [illegible: 1 word]