Joshua 10:32
And the Lord delivered Lachish into the hand of Israel, which took it on the second day, and smote it with the edge of the sword, and all the souls that were therein, according to all that he had done to Libnah.
Cross-reference
Joshua 10:30 records the same pattern of total destruction for Libnah — this verse for Lachish follows the identical formula.
Joshua 10:28 describes the same total destruction at Makkedah — both verses follow the same pattern for different cities.
Joshua 10:35 explicitly says they did to Eglon 'just as they had done to Lachish' — a direct narrative link.
Joshua 12:11 lists the king of Lachish among conquered kings — a direct record of this same victory.
Joshua 15:39 lists Lachish as a city allotted to Judah — the conquest here leads to its later allocation.
Joshua 11:12 summarizes the conquest of northern cities with total destruction — a general parallel to the specific action here.
Deuteronomy 7:2 commands total destruction of Canaanite nations — this verse's execution of that command at Lachish fulfills it.