Charles Ellicott Commentary Exodus 15:19

"For the horses of Pharaoh went in with his chariots and with his horsemen into the sea, and Jehovah brought back the waters of the sea upon them; but the children of Israel walked on dry land in the midst of the sea." — Exodus 15:19 (ASV)

This verse is parenthetical. It forms no part of the “Song of Moses.” Originally, perhaps, when that song was a separate document, it was appended as a historical comment, showing the occasion on which the poem was composed.

When the records of Moses were collected—either by himself, towards the close of his life, or by Joshua—the addition was kept, although it had become unnecessary for the original purpose. As it stands, it emphasizes the great fact of Israel’s final deliverance—the nucleus around which Exodus gathers itself.