וּמֹשֶׁ֣ה וְאַהֲרֹ֗ן עָשׂ֛וּ אֶת־כָּל־הַמֹּפְתִ֥ים הָאֵ֖לֶּה לִפְנֵ֣י פַרְעֹ֑ה וַיְחַזֵּ֤ק יְהוָה֙ אֶת־לֵ֣ב פַּרְעֹ֔ה וְלֹֽא־שִׁלַּ֥ח אֶת־בְּנֵֽי־יִשְׂרָאֵ֖ל מֵאַרְצֽוֹ׃ (פ)
A Mojżesz i Ahron spełnili wszystkie te cuda przed Faraonem; ale ukrnąbrnił Wiekuisty serce Faraona i nie uwolnił synów Israela z ziemi swojej.
Akeidat Yitzchak
The observation about G-d having hardened the spirit of Sichon King of the Emorites, which was referred to earlier, is to be understood in a similar vein. Sichon, who had observed that Israel seemed to have avoided battling the Moabites or the Edomites and had detoured around their respective countries, concluded that Israel's motive had been fear. Thus he felt encouraged to assume a militant posture. This resulted in his defeat and the conquest of his lands by the Israelites. But there had been no interference with his freedom of choice.