(the two Sipparas) is mentioned by Sennacherib in his letter to Hezekiah as a city whose king had been unable to resist the Assyrians (2 Kings 19:13; Isaiah 37:13; comp. 2 Kings 18:34). It is identified with the famous town of Sippara on the Euphrates above Babylon, which was near the site of the modern Mosaib. The dual form indicates that there were two Sipparas, one on either side of the river. Berosus celled Sippara “a city of the sun;” and in the inscriptions it bears the same title, being called Tsipar sha Shamas, or “Sippara of the Sun”—the sun being the chief object of worship there (comp. 2 Kings 17:31).
Smith's Bible Names Dictionary (1866)