The heads of the ancestral clan of Gilead son of Makir, the son of Manasseh--they were from the clans of the descendants of Joseph--approached Moses and the leaders who were heads of the families in the People of Israel.
They said, "When GOD commanded my master to hand over the inheritance-lands by lot to the People of Israel, my master was also commanded by GOD to hand over the inheritance-land of Zelophehad our brother to his daughters.
But what happens if they marry into another tribe in the People of Israel? Their inheritance-land will be taken out of our ancestral tribe and get added into the tribe into which they married.
And then when the Year of Jubilee comes for the People of Israel their inheritance will be lumped in with the inheritance of the tribe into which they married--their land will be removed from our ancestors' inheritance!"
Every daughter who inherits land, regardless of the tribe she is in, must marry a man from within her father's tribal clan. Every Israelite is responsible for making sure the inheritance stays within the ancestral tribe.
These are the commands and regulations that GOD commanded through the authority of Moses to the People of Israel on the Plains of Moab at Jordan-Jericho.