Numbers 36:9
Neither shall the inheritance remove from one tribe to another tribe; but every one of the tribes of the children of Israel shall keep himself to his own inheritance. Neither shall the inheritance remove from one tribe to another tribe; but every one of the tribes of the children of Israel shall keep himself to his own inheritance.
Numbers 36:9 stands in the closing chapters of Numbers as part of the law concerning the marriage of heiresses. It belongs to the provisions governing the inheritance of daughters. Its setting is the regulation of how landed property is to be preserved when daughters inherit.
The requirement is that landed inheritance remain within its own tribe and not be removed from one tribe to another. No tribal inheritance is to pass over into another tribe. Each one of the tribes of the children of Israel is to keep itself to its own allotted inheritance.