וַיְחַזֵּ֥ק יְהוָ֖ה אֶת־לֵ֣ב פַּרְעֹ֑ה וְלֹ֥א שִׁלַּ֖ח אֶת־בְּנֵ֥י יִשְׂרָאֵֽל׃ (פ)
But the LORD hardened Pharaoh’s heart, and he did not let the children of Israel go.
Read Jewish philosophical commentary on Exodus 10:20: and classical philosophical sources.