וַיְחַזֵּ֣ק יְהֹוָ֗ה אֶת־לֵ֤ב פַּרְעֹה֙ מֶ֣לֶךְ מִצְרַ֔יִם וַיִּרְדֹּ֕ף אַחֲרֵ֖י בְּנֵ֣י יִשְׂרָאֵ֑ל וּבְנֵ֣י יִשְׂרָאֵ֔ל יֹצְאִ֖ים בְּיָ֥ד רָמָֽה׃
And the LORD hardened the heart of Pharaoh king of Egypt, and he pursued after the children of Israel; for the children of Israel went out with a high hand.
Read kabbalistic (mystical) interpretation of Exodus 14:8: and classical mystical sources.