Soon after the Israelites’ conquest of the trans-Jordan, the Machirites (descendants of Manasseh) came to Moses in order to raise the issue of Zelophehad’s inheritance.
Zelophehad had only fathered daughters.
Hence, if his daughters married Israelites from a different tribe, the Machirites would lose a sizeable chunk of their land-inheritance.
At first blush, the Machirites’ concern seems reasonable enough.