Majma al-Zawaid — Hadith 8946

Fadalah bin Abi Fadalah narrates (Sayyiduna Abu Fadalah (may Allah be pleased with him) was one of the people of Badr): I went with my father (Sayyiduna Abu Fadalah (may Allah be pleased with him)) to visit Sayyiduna Ali bin Abi Talib (may Allah be pleased with him) during an illness of his that had become severe. My father said to him: "What keeps you in this place of yours? If your death were to come, none would attend to you but the Bedouins of Juhaynah. Have yourself carried to Madinah, for if your death comes there, your companions will attend to you and offer your funeral prayer." Sayyiduna Ali (may Allah be pleased with him) said: "The Prophet (peace and blessings be upon him) took a covenant from me that I will not die until I am made a ruler, and then this (Sayyiduna Ali (may Allah be pleased with him) said this pointing to his beard) will be dyed from this (that is, Sayyiduna Ali (may Allah be pleased with him) said this pointing to his head; meaning my beard will be dyed with the blood of my head)." (The narrator says:) Later Sayyiduna Ali (may Allah be pleased with him) was martyred, and Sayyiduna Abu Fadalah (may Allah be pleased with him) was also martyred fighting on the side of Sayyiduna Ali (may Allah be pleased with him) at the Battle of Siffin.
Ahmad recorded it; its chain contains Abdullah bin Muhammad bin Aqil, who is hasan al-hadith (good in hadith), and the rest of its narrators are thiqat (trustworthy).