Rashi on Exodus 14:25/רש"י על שמות י״ד:כ״ה

1‎ויסר את אפן מרכבותיו AND HE REMOVED THEIR CHARIOT WHEELS — Through the power of the fire of the pillar of fire the wheels were burnt and the chariots were thus dragged along and those who were sitting in them were thrown about and their limbs were all put out of joint (cf. Mekhilta).

2וינהגהו בכבדות signifies: And He treated them with a treatment that was hard and harsh to them. In the measure that they (the Egyptians) had meted out to the Israelites was it meted out to them, for (9:34) “He hardened his heart, he and his servants”, and therefore here: “He treated them (the Egyptians) in a hard manner” (cf. Mekhilta).

3נלחם להם במצרים FIGHTETH FOR THEM במצריים — means against the Egyptians. Another explanation of במצרים is: in the land of Egypt, for just as these were smitten at the Sea so, too, were smitten those who remained in Egypt (cf. Mekhilta).