Joshua 10:30
And the Lord delivered it also, and the king thereof, into the hand of Israel; and he smote it with the edge of the sword, and all the souls that were therein; he let none remain in it; but did unto the king thereof as he did unto the king of Jericho.
Cross-reference
Joshua 10:28 records the conquest of Makkedah with the exact same formula — smite, destroy all, treat king as Jericho's — immediately before Libnah.
Joshua 10:32 recounts Lachish's conquest, explicitly modeled on Libnah — 'according to all that he had done to Libnah'.
Joshua 8:24 describes the total destruction of Ai — smiting all inhabitants with the sword, identical to the method used at Libnah.
Joshua 11:12 summarizes northern conquests with the same language of smiting with the sword and utter destruction as seen at Libnah.
Joshua 12:15 lists the king of Libnah among conquered kings, confirming his defeat recorded in this verse.
Deuteronomy 2:33 recounts God delivering Sihon into Israel's hand — the same divine victory pattern as the conquest of Libnah.
Deuteronomy 7:2 commands utter destruction of Canaanites, which Joshua carries out by leaving no survivors in Libnah.