Musnad Ahmad 775:21

Abu al-Nadr narrated to us, al-Hashraj ibn Nabatah al-'Absi, a Kufan, narrated to me, Sa'id ibn Jumhan narrated to me, he said: I came to 'Abdullah ibn Abi Awfa while he had lost his sight, and I greeted him. He said to me: "Who are you?" I said: "I am Sa'id ibn Jumhan." He said: "And what became of your father?" I said: "The Azariqah killed him." He said: "May Allah curse the Azariqah, may Allah curse the Azariqah. The Messenger of Allah (ﷺ) narrated to us that 'they are the dogs of Hellfire.'" I said: "The Azariqah alone, or the Khawarij in their entirety?" He said: "Rather, the Khawarij in their entirety." I said: "But the ruler oppresses the people and does [such and such] to them." He took my hand and squeezed it firmly with his hand, then said: "Woe to you, O son of Jumhan! You must stick to the great majority (al-sawad al-a'zam), you must stick to the great majority. If the ruler listens to you, then go to him in his house and inform him of what you know. If he accepts from you, [then good], and if not, then leave him, for you are not more knowledgeable than him."