“Whoever Causes Ali pain, causes me pain.”
Hazrat Amr (ra) bin Shas Aslami, who was part of the Treaty of Hudaibiyyah, states: “On one occasion, I travelled to Yemen with Hazrat Ali (ra). During the journey he dealt with me in a strict manner and I began to harbour grievances against him. Thus, when we returned from Yemen, I complained about him in the mosque and the Holy Prophet (sa) came to know about my complaint. One day, when I entered the mosque, the Holy Prophet (sa) was sitting with a few of his companions. When the Holy Prophet (sa) saw me, he observed me closely.” He further narrates, “The Holy Prophet (sa) looked towards me intently. When I sat down, the Holy Prophet (sa) said, ‘O Amr! By God, you have caused me pain!’ I replied, ‘O Messenger (sa) of Allah! I seek refuge in Allah from that which causes you pain.’ The Holy Prophet (sa) said, ‘Certainly whoever causes Ali pain, causes me pain.’” This is a narration of Musnad Ahmad bin Hanbal.
(Ahmad bin Hanbal, Musnad Ahmad bin Hanbal, Vol. 5, Hadith Amr bin Shas, Hadith 16056 [Beirut, Lebanon: Alam al-Kutub, 1998], 478-479)