Deu 2:26-36 “So I sent messengers from the wilderness of Kedemoth to Sihon the king of Heshbon, with words of peace, saying, ‘Let me pass through your land. I will go only by the road; I will turn aside neither to the right nor to the left. You shall sell me food for money, that I may eat, and give me water for money, that I may drink. Only let me pass through on foot, as the sons of Esau who live in Seir and the Moabites who live in Ar did for me, until I go over the Jordan into the land that the LORD our God is giving to us.’ But Sihon the king of Heshbon would not let us pass by him, for the LORD your God hardened his spirit and made his heart obstinate, that he might give him into your hand, as he is this day. And the LORD said to me, ‘Behold, I have begun to give Sihon and his land over to you. Begin to take possession, that you may occupy his land.’ Then Sihon came out against us, he and all his people, to battle at Jahaz. And the LORD our God gave him over to us, and we defeated him and his sons and all his people. And we captured all his cities at that time and devoted to destruction every city, men, women, and children. We left no survivors. Only the livestock we took as spoil for ourselves, with the plunder of the cities that we captured. From Aroer, which is on the edge of the Valley of the Arnon, and from the city that is in the valley, as far as Gilead, there was not a city too high for us. The LORD our God gave all into our hands.
Because of this refusal, Israel fought a battle recorded in Numbers 21. They simply asked for safe passage through the land of the Amorites, but they were refused. God worked behind the scenes in hardening the heart of Sihon, the King of the Amorites. It was right for God to do this because the Creator has the right to do whatever He pleases with His creatures. But it was also right because of the way God did it. God did not persuade a reluctant Sihon to act out against Israel; God simply let Sihon’s heart take the evil way it wanted to take. God did not change Sihon’s heart from good to bad but hardened it in its malice towards Israel. God hardened the heart of Sihon. God led Sihon into the destructive course that his heart desired so that the land of the Amorites became the possession and inheritance of Israel. The war against the Amorites was one of the unique wars of judgment God told Israel to fight. In it, Israel was not just to defeat the Amorites on the field of battle, but to bring judgment against their whole society. Thirty-eight years before, Israel refused to go into the Promised Land because they felt they were over-matched militarily. Here, when they began to enter the land by faith, God showed them how it could have been 38 years before – if they had only believed Him. “there was not one city too high for us.” The high walls of the Canaanite cities had intimidated Israel 38 years before (see Deuteronomy 1:28). But walking in faith, they were now nothing before the LORD. (Guzik)