It is reported about Sayyiduna Abu Juhayfah (may Allah be pleased with him) that he came to Sayyiduna Ali (may Allah be pleased with him). Sayyiduna Ali (may Allah be pleased with him) called for his sword and took out from inside the sword a piece of leather on which there was Arabic writing. He said: The Prophet (peace and blessings be upon him) left nothing besides the Book of Allah; whatever was revealed, he conveyed it, except for this thing. In it was written: "In the name of Allah, the Most Gracious, the Most Merciful. The Messenger of Allah, Sayyiduna Muhammad (peace and blessings be upon him), said: Every prophet has a sanctuary (haram), and my sanctuary is Madinah."
Imam al-Tabarani recorded it in al-Mu'jam al-Awsat; its narrators have been declared trustworthy, though some of them have been criticised.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الحج / 5793