Sayyiduna Ka'b bin Ujrah (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) said: "Do not revile Ali, for he is utterly heedless of himself where the Essence of Allah is concerned."
Al-Tabarani recorded this narration in al-Mu'jam al-Kabir and al-Mu'jam al-Awsat. Its chain contains a narrator, Sufyan bin Bishr, or perhaps Bashir, a later narrator who is not the one who narrated from Abu Abd al-Rahman al-Hubuli, and I do not know him. The rest of its narrators have been declared trustworthy, though there is weakness in some of them.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب المناقب / 14743
Hadith Gradingمحدثین:إسنادہ ضعیف
Hadith Takhrij«اخرجه الطبراني فى المعجم الكبير (148/19) ، أخرجه المعجم الأوسط للطبراني برقم: 9357»