Hadith No: 2
Al-Muttaqi al-Hindi - Kanz al-‘Ummal fi Sunan al-Aqwal wal-Af'al
Volume: (13) - Page Number: (123/124)
36394 - From Urwah: That a man spoke ill of Ali in the presence of Umar. Umar said, "Do you know the owner of this grave, Muhammad ibn Abdullah ibn Abd al-Muttalib, and Ali ibn Abi Talib ibn Abd al-Muttalib?
Do not mention Ali except in good, for if you harm him, you will be harming this one in his grave."