Muwatta Malik, Book 8, Hadith 314 (In-Book) ⓘ
Yahya related to me from Malik that he had heard that Urwa ibn az-Zubayr and Said ibn al-Musayyab used to pray voluntary prayers sitting.
وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ عُرْوَةَ بْنَ الزُّبَيْرِ، وَسَعِيدَ بْنَ الْمُسَيَّبِ، كَانَا يُصَلِّيَانِ النَّافِلَةَ وَهُمَا مُحْتَبِيَانِ .
also referenced under: Book 8, Hadith 25 (USC-MSA)