The remnant of Benjamin must be preserved. An entire Israelite tribe should not be wiped out.
Referenced Verses
Num 26:55 : 55 The land must be divided by lot; and they will inherit in accordance with the names of their ancestral tribes.
Num 36:7 : 7 In this way the inheritance of the Israelites will not be transferred from tribe to tribe. But every one of the Israelites must retain the ancestral heritage.