Musannaf Ibn Abi Shayba 3:3593

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Mis’ar, from ‘Amr ibn Murrah, from Abu ‘Ubaydah, who said: The prayer of ‘Abdullah [ibn Mas’ud] which he would not abandon from the voluntary prayers was four [rak’ahs] before the Dhuhr and two [rak’ahs] after it, and two [rak’ahs] after the Maghrib, and two [rak’ahs] after the ‘Isha, and two [rak’ahs] before the Fajr.