Silsilat al-Ahadith al-Sahihah

Ziyadah bin ‘Ilaqah narrates from his uncle that Sayyiduna Mughirah bin Shu‘bah (may Allah be pleased with him) spoke ill of Sayyiduna ‘Ali bin Abi Talib (may Allah be pleased with him). Sayyiduna Zayd bin Thabit (may Allah be pleased with him) went to Sayyiduna Mughirah (may Allah be pleased with him) and said: O Mughirah! Do you not know that the Messenger of Allah (peace and blessings be upon him) forbade reviling the dead? So why do you insult Sayyiduna ‘Ali (may Allah be pleased with him) after his death?