Kommentar zu Dewarim 2:30

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."

כי הקשה ה' אלו-היך את רוחו ואמץ את לבבו, “for the Lord your G’d hardened his spirit and made his heart stubborn.” This kind of language is employed only when the people concerned are wicked in the extreme and beyond redemption. Pharaoh was another example of such a person whom G’d deprived of his free will as a penalty for abusing it so grossly. (Compare Maimonides Hilchot Teshuvah 6,3). Seeing that these people’s sins were not outgrowths of an overpowering urge, but were based on a deliberate attempt to thwart G’d, they are denied the opportunity to repent at a certain stage in their lives. Even when they are emotionally ready to repent, G’d causes some event which make their minds resist such attempts. You will find that the Torah does not mention such an attempt by G’d to prevent Pharaoh from true repentance until after he had already failed to repent and his promise four times (compare Exodus 7,13; 8,11; 8,28; 9,7;). We find something similar in Kings I 18,37 where Elijah refers to G’d having caused the hearts of the people of Israel as turning away from Him as a punishment for their many and repeated sins (Maimonides Hilchot Teshuvah 6,3).

V. 30. כי הקשה ד׳ אלהיך (siehe zu Schmot Kap. 14, 3 u. 4). Auch hier dürfte Sichon aus dem Verhalten Israels gegen Ammon und Moab, insbesondere aus ihrem Umgehen des edomitischen Gebietes, durch welches sie den kürzesten Weg ins Land gehabt hätten, Veranlassung zum Widerstand und Kampfesmut geschöpft haben. הקשה: zum Widerstand, ואמץ את לבבו: zum Angriff.

ואמץ את לבבו, in order to make war against them.