Musar על יהושע 2:18

The spies reversed the true state of affairs by reporting that the inhabitants had merits, implying Israel did not have sufficient merits. They committed one sin after another, until in the end they denied the virtues of G–d by implying that these inhabitants were mightier than G–d Himself, when they said in 13,31: "for it is stronger than He," (referring to G–d when they said ממנו.) When Joshua sent out his spies, they repaired the damage done by the ten spies in our story. That is the deeper significance of the red line that they demanded that Rahab should suspend the rope outside her window (Joshua 2,18).