Numbers 16:1

Now Korah, the son of Izhar, the son of Kohath, the son of Levi, and Dathan and Abiram, the sons of Eliab, and On, the son of Peleth, sons of Reuben, took men:

Now Korah, the son of Izhar, the son of Kohath, the son of Levi,.... A great grandson of Levi's, and own cousin to Moses and Aaron, being brothers children; for Amram the father of Moses and Aaron, and Izhar the father of Korah, were own brothers, both of them the sons of Kohath, and Amram the eldest, and Izhar the next, Exodus 6:16; this man is mentioned first, being the contriver, and plotter, and ringleader of the following sedition, and which is called "the gainsaying of Core", Jude 1:11; when this was made is not certain; Aben Ezra thinks this affair happened in the wilderness of Sinai, when the firstborn were exchanged, and the Levites were separated for holy service, Numbers 3:1; but, according to the Targum of Jonathan, it was after the law concerning the fringes was given, which it here follows, and was on that account; for it says, that Korah took his coat, which was all blue, and that the men with him rose up, and in the face of Moses taught the rite concerning the blue ribbon; when Moses declared he had it from God, that the fringe should be of white, and one thread of blue should be in it; but Korah and his company made their coats and fringes all of blue, which the Lord commanded not: but what Korah is said to take is either himself, or men, or both, and not clothes, as follows:

and Dathan and Abiram, the sons of Eliab, and On the son of Peleth,

sons of Reuben, took men; which men are described in Numbers 16:2, even princes of the assembly, &c. or he, Korah, took himself, as Ben Melech, or divided himself, as Onkelos, separated himself from the congregation, and set himself at the head of a party he gathered together; and the "vau" or "and" before "Dathan" may be additional or superfluous, as Chaskuni observes, and so Abendana; and then the sense is, that Korah took Dathan, Abiram and On, apart by themselves, and entered into a consultation and confederacy with them against Moses and Aaron, with whom he was offended on account of the priesthood being bestowed on the latter by the former; and these men he associated to him, being the sons of Reuben, who would the rather listen to him, and join with him, because the right of the firstborn was taken from them, and the camp of Judah was placed before them; and with these men he could more easily commune, because the camp of Reuben and the Kohathites lay on the same side of the tabernacle, Numbers 2:10; Eliab, the father of Dathan and Abiram, was the son of Pallu, the second son of Reuben,

Numbers 26:5; but as for On, no mention is made of him elsewhere, nor any more in this place; it is thought he separated from his company after he had heard what Moses said to them; and the Rabbins say, his wife delivered him out of their hands, as Abendana observes.