Exodus 15:19 - Ellicott's Commentary On The Whole Bible

This verse is parenthetic. It forms no part of the “Song of Moses.” Originally, perhaps, when that song was a separate document, it was appended as an 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 emphasises the great fact of Israel’s final deliverance — the nucleus around which Exodus gathers itself.