Contention against leadership is contagious, and contentious people work hard to convince their companions to join their cause. Korah's initial grievances against Moses and Aaron had nothing to do with the Reubenites, but through frequent conversation and the subtle manipulation of ideas, Korah was able to draw his neighbors into sedition.
Korah the son of Izhar ... and On the son of Peleth ... (Numbers 16:1)
Three chief Reubenites joined with Korah in his rebellion against Moses: Dathan, Abiram and On. Dathan and Abiram met a grim fate for their part in the rebellion, but On was apparently spared. The Talmud tells a story to explain how the rebellion started and how it was that On was spared from judgment (b.Sanhedrin 109b-110a).
According to the story, Korah's rebellion began at his wife's instigation. She resented Moses for assigning her Levite husband the lowly status of servant. She was jealous of the wives of Aaron's household who were married to prestigious priests. So she began to subtly undermine her husband's loyalty toward Moses and Aaron. She would nag at him, saying, "See what Moses has done? He has made himself king and appointed his brother as high priest and his nephews as priests. He orders everyone to set aside portions for the priests."
Every day when Korah came back from the assembly, his wife asked him what Moses had said, and then she would ridicule his teachings. For example, when Korah told her, "Moses taught us to attach threads of blue to the tassels on the four corners of our garments," she retorted, "Moses is not hearing from God; he is just making things up. Go ask Moses if you need to attach blue threads to a garment that is completely made of blue fabric." She constantly criticized Moses and Aaron and the commandments. "Can't you see that Moses is making a fool of you and the other Levites?" she would ask. When Korah finally decided to raise a rebellion, he thought it was his own initiative, but his wife had planted the ideas in his head.
The wife of On the Reubenite was just the opposite. When she found out that her husband had joined Korah's insurrection against Moses and Aaron, she took him aside and asked, "Why are you getting involved with these Levites? What business is it of yours? You are a student of Moses. If Korah deposes him, you will be a student of Korah. How does that improve your situation? As it is, you have gotten yourself into matters in which you should not be involved." Her husband explained that he had been swept away with Korah's rhetoric and taken a vow to join him in a rebellion the next morning. "Do as I say and I will get you out of your vow," she said. She fed him a rich meal and gave him plenty of wine so that he overslept. When Korah's men came looking for him, she sat in the doorway of the tent, brushing her hair, and did not let them into the tent to wake him. So her husband, On, missed the entire affair without intentionally breaking his vow.
The story is just a folk tale, but it has an important lesson about how we influence our spouses and how we allow them to influence us. Proverbs 14:1 says, "The wise woman builds her house, but the foolish tears it down with her own hands." According to the Talmud, the wise woman is like the wife of On, but the foolish woman is like the wife of Korah.