The judgment on Canaan came from God, not Israel. God had shown mercy to the people of Canaan for many generations. However, God decided that "iniquity of the Amorites" now requires that they become set apart for destruction (Genesis 15:16). Therefore, he decided to harden their hearts (to make them stubborn and unwilling to change). God used Israel as the tool and agent of his judgment. In later centuries, God used other nations to judge Israel and Judah for their sins.