Musnad Ahmad 240:1

Ya'qub ibn Ibrahim narrated to us, my father narrated to us, Muhammad ibn Ishaq narrated to us, from Aban ibn Salih, from al-Fadl ibn Ma'qil ibn Sinan, from 'Abdullah ibn Niyar al-Aslami, from 'Amr ibn Shas al-Aslami, who said—and he was among the companions of al-Hudaybiyyah—he said: I went out with 'Ali to Yemen, and he treated me coldly during that journey, until I felt resentment toward him in my heart. When I arrived, I expressed my complaint about him in the mosque, until that reached the Messenger of Allah, peace and blessings of Allah be upon him. One morning, I entered the mosque while the Messenger of Allah, peace and blessings of Allah be upon him, was among a group of his companions. When he saw me, he fixed his eyes upon me—meaning he stared at me—until, when I sat down, he said: "O 'Amr, by Allah, you have harmed me." I said: "I seek refuge in Allah from harming you, O Messenger of Allah." He said: "Yes, whoever harms 'Ali has indeed harmed me."