Sahih al-Bukhari, Book 62, Hadith 112 (In-Book) ⓘ
Narrated Ibn Abi Mulaika: Somebody said to Ibn `Abbas, "Can you speak to the chief of the believers Mu`awiyah, as he does not pray except one rak`a as witr?" Ibn `Abbas replied, "He is a Faqih (i.e. a learned man who can give religious verdicts)."
حَدَّثَنَا ابْنُ أَبِي مَرْيَمَ، حَدَّثَنَا نَافِعُ بْنُ عُمَرَ، حَدَّثَنِي ابْنُ أَبِي مُلَيْكَةَ، قِيلَ لاِبْنِ عَبَّاسٍ هَلْ لَكَ فِي أَمِيرِ الْمُؤْمِنِينَ مُعَاوِيَةَ، فَإِنَّهُ مَا أَوْتَرَ إِلاَّ بِوَاحِدَةٍ. قَالَ إِنَّهُ فَقِيهٌ.
also referenced under: Hadith 3765 (DarusSalam) & Volume 5, Book 57, Hadith 109 (USC-MSA)