Musannaf Ibn Abi Shayba 3:2505

Humaid ibn Abd al-Rahman narrated to us, from Zuhayr, from Abu Ishaq, who said: I saw al-Harith ibn Abi Rabi'ah pray two rak'ahs in the chamber during the forenoon (duha) when he intended to set out for the water of Himyar. A group of people prayed with him, among them was al-Aswad ibn Yazid.