The leaders of the tribe of Manasseh faced a complex legal and territorial dilemma regarding the laws of inheritance. Following the ruling that daughters inherit their father's estate when he leaves no sons, a new concern emerged about land permanently shifting between tribes through marriage. If these women were to marry men from other Israelite tribes, the land they inherited would eventually pass into the possession of their husbands' tribes. This happens because while sons inherit their mother's property, their tribal identity is determined entirely by their father [רש״י, רש ר הירש]. This issue would become even more severe if the women married, passed away, and left heirs before the land was physically divided. In such a case, territory originally meant for Manasseh would be handed over to a different tribe during the very first distribution [רש ר הירש].
The tribal leaders presented a two-layered argument, addressing both personal and national concerns. On a private and familial level, land was distributed according to the number of people in each family. If these women married outside their tribe, their family's specific portion would be reduced and transferred to an outside family [מלבי״ם].
On a broader level, the leaders also expressed concern over the land that would be added to the other tribes. While it might seem unusual to worry about another tribe's gain rather than just their own loss, this addition would severely disrupt the established borders and the divine lottery system. Geographically, the lottery was designed to define a clear, continuous area for each tribe. Transferring ownership would create foreign enclaves within the territory of Manasseh, fracturing the physical integrity of the tribe's borders [מלבי״ם].
Furthermore, this disruption carried deep spiritual consequences. The holiness of the land depended on each tribe settling in the exact location determined for them by the lottery. Altering this distribution would damage the spiritual perfection of the land, which God intended to establish specifically through this lottery system. For this reason, the leaders carefully emphasized the disruption to the lottery itself, rather than just focusing on the loss of physical property [העמק דבר].