2 Kings 19:21 - Joseph Benson’s Commentary on the Old and New Testaments

The daughter of Zion That is, Jerusalem; which is called the daughter of Zion, say some, because the hill of Zion, as being the strongest and safest part, was first inhabited, and by the increase of inhabitants, Jerusalem arising around, as it were, sprang from it, and might therefore properly enough be termed its daughter. But it is more probable that the people of Zion, or of Jerusalem, (Zion, an eminent part of the city, being put for the whole,) are here termed its daughter, cities and countries being often called mothers, and their inhabitants daughters. Thus we read of the daughter of Babylon, the daughter of Tyre, &c., Psalms 137:8; Psalms 45:13. Zion or Jerusalem is termed a virgin, because she was pure in good measure from that gross idolatry wherewith other people were defiled, which is called spiritual whoredom; and to signify that God would defend her from the rape which Sennacherib intended to commit upon her, with no less care than parents do their virgin daughters from those who seek to force and deflour them. The image is extremely fine, whereby the contempt of Sennacherib's threats is expressed.