פּירוש אויף דברים 2:30

“Because the Lord had stiffened his will” [2:30]. Sihon did not want to allow Israel into his land, because the Holy One had incited him so that he would not allow Israel to go into his land, expecting that Israel should destroy him because he would not let him go through his land. People ask: if the Holy one had incited him that he should not allow Israel to go through his land, what kind of evil did he do when he did not let them go, when God incited him and placed in his heart that he should not allow Israel to go through, what was Sihon guilty of? The explanation is that when the Holy One sees that the evildoer did evil, three or four times, the Holy One incites him further to do evil, expecting that he will not repent and should be destroyed. If he should want to repent, then the Holy One puts it into his mind that he should continue to do evil so that he should be destroyed. The Holy One did the same to Pharaoh.

כי הקשה ה' אלוקיך את רוחו, in order for him to refuse to allow the Israelites to traverse his territory.

ולא אבה פיחון…העבירנו בו, "and Sichon did not want us to traverse it, etc." Whenever the expression לא אבה is used it describes a refusal without an adequate reason being offered. Although Sichon had no reason to fear that the Israelites would infringe on any of his rights and he was convinced that the Israelites were physically unable to cause him any harm, he still refused to let them pass. This is why the Torah had to provide the reason, i.e. כי הקשה ה׳ את רוחו, "G'd helped his spirit to be obstinate."