Charles Ellicott Commentary Exodus 15:16

"Terror and dread falleth upon them; By the greatness of thine arm they are as still as a stone; Till thy people pass over, O Jehovah, Till the people pass over that thou hast purchased." — Exodus 15:16 (ASV)

Fear and dread shall fall upon them. — A portion of the Edomites felt so much fear of Israel that they allowed them to pass through their territory (Deuteronomy 2:4). The Moabites of Ar did similarly (Deuteronomy 2:29).

Till your people pass over — i.e., cross the frontier of the Canaanites and enter their country. There is no need to suppose that Moses had yet any distinct idea of the place where the frontier would be crossed.