World Wide Study Bible
a Bible passage
He has raised up a mighty savior for us
in the house of his servant David,
69. horn of salvation—that is "strength of salvation," or "mighty Salvation," meaning the Saviour Himself, whom Simeon calls "Thy Salvation" (Lu 2:30). The metaphor is taken from those animals whose strength is in their horns (Ps 18:2; 75:10; 132:17).
house of … David—This shows that Mary must have been known to be of the royal line, independent of Joseph; of whom Zacharias, if he knew anything, could not know that after this he would recognize Mary.