In The Name of Allaah, The Most Merciful, The Bestower of Mercy.

Narrated Ibn Abee Mulaikah [may Allaah have mercy upon him] who said, “Mu’aawiyah [may Allaah be pleased with him and his father] offered one rak`’ah of Witr prayer after the `Isha prayer, and at that time a freed slave of Ibn `Abbaas [may Allaah be pleased with him and his father] was present. He (i.e. the slave) went to Ibn `Abbas (and told him that Mu’aawiyah offered one rak’ah of Witr prayer). Ibn Abbas said, “Leave him, for he was in the company of Allah’s Messenger (ﷺ).” [Saheeh Al-Bukhaari. Number 3764]

Narrated Ibn Abi Mulaikah: Somebody said to Ibn Abbas, “Can you speak to the chief of the believers Mu’aawiyah, because he does not pray except one rak’ah as witr?” Ibn `Abbas replied, “He is a Faqih (a learned man with sound understanding and fear of Allaah). [Saheeh Al-Bukhaari. Number 3765]

Shaikhul Islaam Ibn Taymiyyah [may Allaah have mercy upon him] said:

Indeed, it has been established by way of Mutawaatir transmissions that the Prophet [peace and blessings of Allaah be upon him] did give Mu’aawiyah [may Allaah be pleased with him and his father] a position of authority (in an affair) just as he gave authority to others. He (Mu’aawiyah) performed Jihaad with the Prophet and was considered trustworthy by the Prophet to write the revelation for him. The Prophet did not accused him of anything with regards to his writing and Umar Ibn Al-Khattab [may Allaah be pleased with him] – who was one of those well informed regarding the affair of men and Allaah manifested truth from his tongue and heart – never accused Mu’aawiyah of anything in his position of authority. [Majmoo Al-Fataawaa 4/472]

Umar Bin Abdil Azeez [may Allaah have mercy upon him] and his justice was mentioned in the presence of Al-A’mash [may Allaah have mercy upon him], so he said, “Then how about if you lived during the time of Mu’aawiyah [may Allaah be pleased with him and his father]? They said, “O Abu Muhammad! Do you mean in his forbearance?” He said, “No, by Allaah; rather his justice”. [As-Sunnah By Al-Khallaal. 1/437]

On the authority of Al-Jarrah Al-Mawsulee [may Allaah have mercy upon him] who said, “I heard a man ask Al-Ma’aafee Bin Imran [may Allaah have mercy upon him], saying, ‘O Abu Mas’ood! Where is Umar Bin Abdul Aziz compared to Mu’aawiyah Bin Abee Sufyan?’ I saw him become very angry, then he said, ‘No one can be compared to the companions of Muhammad. Mu’aawiyah [may Allaah be pleased with him and his father] is one the Prophet’s scribes, companions, brothers in law and trustees of the revelation revealed to him (i.e. he was trusted by the Prophet to write down the revelation)”. [Ash-Sahree’ah By Imaam Al-Aajuree 5/2466-2467]

To be continued…InShaaAllaah