Muwatta Imam Malik Book of Prayer in Congregation, Hadith 25

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 .