Musannaf Ibn Abi Shayba 3:1469

Ghundar narrated to us, from Shu'bah, from Ash'ath, who said: I accompanied my father, and al-Aswad ibn Yazid, and 'Amr ibn Maymun, and Abu Wa'il. They used to pray two rak'ahs, then they would pray two rak'ahs after them.