Smith's Bible Dictionary
On. 1. the son of Peleth, and one of the chiefs, of the tribe of Reuben, who took part with Korah, Dathan and Abiram in their revolt against Moses. Numbers 16:1. (B.C. 1491). His name does not again appear in the narrative of the conspiracy, nor is he alluded to when reference is made to the final catastrophe.
(abode or city of the sun).
2. A town of lower Egypt, called Beth-Shemesh in Jeremiah 43:13. On is better known, under its Greek name, Heliopolis. It was situated on the east side of the Pelusiac branch of the Nile, just below the point of the Delta, and about twenty miles northeast of Memphis. The chief object of worship at Heliopolis was the sun, whose temple, described by Strabo, is now only represented by the single beautiful obelisk, of red granite, 80 feet 2 inches high, above the pedestal which has stood for more than 4000 years, having been erected by Usirtesen, the second king of the twelfth dynasty.
Heliopolis was anciently famous for its learning, and Eudoxus and Plato studied under its priests. The first mention of this place in the Bible, is in the history of Joseph, to whom we read, Pharaoh gave "to wife, Asenath, the daughter of Potipherah, priest of On." Genesis 41:45. Compare Genesis 41:60 and Genesis 46:20.
(On is to be remembered, not only as the home of Joseph, but as the traditional place to which, his far-off namesake took Mary and the babe Jesus in the flight to Egypt.
The two famous obelisks, long called "Cleopatra's Needles," one of which now stands in London, and the other in Central Park in New York city, once stood before this city, and were seen by the children of Israel, before the Exodus, having been quarried at Syene on the Nile, erected at On, (Heliopolis), by Thothmes III, B.C. 1500, and inscriptions added by Rameses II, (Sesostris), two hundred years later. They were taken to Alexandria, by Augustus Caesar A.D. 23, from which they were removed, to their present places. - Editor).
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Smith, William, Dr. Entry for 'On'. Smith's Bible Dictionary. https://www.studylight.org/dictionaries/eng/sbd/o/on.html. 1901.