Musannaf Ibn Abi Shaybah

Hazrat Abad bin Mansoor says that I went to the central mosque and saw that the people had not yet performed the Zuhr prayer. While waiting for Zuhr, I started offering nafl (voluntary) prayers. In the meantime, the congregation stood up. When they finished the prayer, I found out that it was the Asr prayer. So I then performed my Zuhr prayer. Then I performed the Asr prayer. Then I went to Hasan and asked him about this issue, and he gave me the same ruling as what I had done.