Sforno on Exodus 15:16/ספורנו על שמות ט״ו:ט״ז

1תפול עליהם אימתה ופחד בגדול זרועך, may it be Your will that fear will overcome them in a manner which will make them flee because they are afraid of Your arm. Moses refers to what the Torah described in 14,25 when the Egyptians announced that they would flee as they realised that G’d was fighting on behalf of Israel.

2ידמו כאבן עד יעבור עמך הן, may it also be Your will that they will not launch an attack against us until we have crossed the rivers still in front of us, i.e. the Arnon and the Jordan, seeing that the battles are always more difficult at river crossings, and we would need greater miracles in order to become victorious. We might not be deserving of such miracles.