Page "Daughters of Zelophehad" Paragraph 3

Later, the family heads of the clan of Manasseh's grandson Gilead appealed to Moses and the chieftains, arguing that if Zelophehad's daughters married men from another Israelite tribe, then their share would be lost to the tribe of Manasseh and be added to the portion of the tribe into which they married.

So Moses, at God's bidding, instructed the Israelites that the plea of the tribal leaders was just and that Zelophehad's daughters could marry anyone they wished, but only among the men of the tribe of Manasseh.