Reason for not Speaking Ill of Hazrat Ali (ra) bin Abi Talib
It is stated in one narration that once, Amir Muawiyyah asked Hazrat Sa‘d (ra), “What stops you from speaking ill of Abu Turab?” This was the title of Hazrat Ali (ra); Hazrat Sa‘d (ra) would never speak ill of him. Hazrat Sa‘d (ra) said, “There are three things which the Holy Prophet (sa) said regarding him – if even one of those things was said about me, it would be dearer to me than red camels. Due to these three things, I will never speak ill of him (i.e., Hazrat Ali (ra)).
“The first is that once, the Messenger (sa) of Allah left Hazrat Ali (ra) behind during an expedition. Upon this, Hazrat Ali (ra) submitted, ‘O Messenger (sa) of Allah! Will you leave me with the women and children?’ The Holy Prophet (sa) replied, ‘Are you not happy at the fact that your connection to me is the same as that of Aaron (as) with Moses (as), except with the difference that you will not be granted the status of prophethood after me.’ The second thing was on the occasion of the Battle of Khaybar, when the Holy Prophet (sa) said, ‘I will give the flag of Islam to such a person who loves Allah and His Messenger (sa) and Allah and His Messenger (sa) love him.’ At the time, we all desired that the flag be given to us for we all had love for the Holy Prophet (sa), however the Holy Prophet (sa) asked for Hazrat Ali (ra) to be brought forward. He did not give it to any of us, but instead said to call for Hazrat Ali (ra). Hazrat Ali (ra) came and he was experiencing an ailment in his eyes at the time. The Holy Prophet (sa) put his blessed saliva from upon his eyes and gave him the flag of Islam. On that day, Allah granted the Muslims victory.
“The third aspect he mentioned was that when this verse was revealed,
فَقُلْ تَعَالَوْا نَدْعُ أَبْنَاءَنَا وَأَبْنَاءَکُمْ وَنِسَاءَنَا وَنِسَاءَکُمْ
(The translation is as follows: “Say [to him], ‘Come, let us call our sons and your sons, and our women and your women.’” [Surah al-e-Imran, Ch.3: V.162])
“the Holy Prophet (sa) called Hazrat Ali (ra), Hazrat Fatima (ra), Hazrat Hassan and Hazrat Hussain (ra) and said, ‘O Allah! These are members of my family.’” This is a narration from Tirmidhi.
(Sunan al-Tirmidhi, Abwab-ul-Manaqib, Hadith no. 3724)