Muwatta Malik Book 8, Hadith 26
Yahya related to me from Malik from Zayd ibn Aslam from al-Qaqa
ibn Hakim that Abu Yunus, the mawla of A'isha, umm al-muminin said,
''A'isha ordered me to write out a Qur'an for her. She said, 'When
you reach this ayat, let me know, "Guard the prayers carefully and the
middle prayer and stand obedient to Allah." ' When I reached it I told
her, and she dictated to me, 'Guard the prayers carefully and the
middle prayer and the asr prayer and stand obedient to Allah.' A'isha
said, 'I heard it from the Messenger of Allah, may Allah bless him and
grant him peace.' "
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.
Yahya related to me from Malik from Zayd ibn Aslam that Amr ibn Rafi said, "I was writing a Qur'an for Hafsa, umm al-muminin, and she said, 'When you reach this ayat, let me know, "Guard the prayers carefully and the middle prayer and stand obedient to Allah." When I reached it I told her and she dictated to me, 'Guard the prayers carefully and the middle prayer and the asr prayer and stand obedient to Allah.' "