20. Harden their hearts. See on Ex. 4:21. God does not exercise arbitrary power to control a person against his will. The case in question has nothing to do with the free moral agency of man, which permits him to choose eternal life and does not prevent his contrary choice. God was here dealing with nations that had already refused His repeated offers of mercy. They had been given ample opportunity for repentance. Now divine justice demanded their prompt execution (see PP 492) and selected the means of their extermination (see Additional Note on ch. 6).
God might have chosen other means for the accomplishment of His judgments upon these nations. His choice of the arms of Israel as His instrument of destruction was for the benefit of the Israelites. They needed to be brought face to face with various tests that would try their faith and prepare them to fulfill their high spiritual destiny. Their failure at Kadesh and the resultant delay in their entry into Canaan had greatly increased the difficulties of the invasion. The Canaanitish nations were thus given ample time to build up their defenses and to prepare their military forces. God intended the extended conquest to be for the discipline of His people, to help them to overcome where formerly they had failed (see PP 437).
No favour. This implies that had these nations repented, God would have shown them favor. Such an attitude is in harmony with His character as expressed in Eze. 33:11 and 2 Peter 3:9. On the other hand, God has a right to destroy those who, having had opportunity for salvation, have not taken advantage of it. Thus He will deal with the finally impenitent. No one may deny Him the right to do the same at any other period in history.