Musannaf Ibn Abi Shayba 37:214

Abu Usama narrated to us, he said: Hisham narrated to us, from his father, who said: Qays ibn Sa'd ibn 'Ubada was with Ali, in charge of his vanguard, and with him were five thousand [men] who had shaved their heads. After Ali died, when al-Hasan entered into a pledge of allegiance with Mu'awiya, Qays refused to enter [into it]. He said to his companions: "Whatever you wish; if you wish, I will fight alongside you forever until the sooner [of us] dies, and if you wish, I will obtain a guarantee of safety for you." They said: "Obtain a guarantee of safety for us." So he obtained for them that they would have such and such, and that they would not be punished for anything, and that he was one of them; and he did not obtain anything specifically for himself. When he departed toward Medina and proceeded with his companions, he began to slaughter a camel for them every day until he reached [it].