On

The name "On" labels two distinct things in the text: an Egyptian city of priestly importance, and a Reubenite who joined Korah's revolt.

The city in Egypt

On appears in the Joseph narrative as the home of Joseph's father-in-law, the priest Poti-phera. When Pharaoh elevates Joseph he gives him a wife from this priestly house: "And Pharaoh called Joseph's name Zaphenath-paneah; and he gave him as wife Asenath, the daughter of Poti-phera priest of On. And Joseph went out over the land of Egypt" (Gen 41:45). The same notice frames the genealogy of Joseph's sons: "And to Joseph in the land of Egypt were born Manasseh and Ephraim, whom Asenath, the daughter of Poti-phera priest of On, bore to him" (Gen 46:20). Both passages locate On in Egypt and identify it as a priestly seat.

The Reubenite of Korah's revolt

A man named On the son of Peleth appears once, listed alongside Korah, Dathan, and Abiram in the conspiracy against Moses: "Now Korah, the son of Izhar, the son of Kohath, the son of Levi, with Dathan and Abiram, the sons of Eliab, and On, the son of Peleth, sons of Reuben, took [men]" (Num 16:1). He is grouped with Dathan and Abiram under "sons of Reuben"; the text names him at the outset of the rebellion and does not return to him afterward.