Rashi on Exodus 14:8/רש"י על שמות י״ד:ח׳

1ויחזק ה׳ את לב פרעה AND THE LORD ALLOWED THE HEART OF PHARAOH TO BE HARDENED — the meaning is, that he was in doubt whether to pursue or not, and He hardened his heart to pursue (Mekhilta).

2ביד רמה WITH A HIGH HAND — with high and open daring (cf. Mekhilta).