Musannaf Ibn Abi Shayba 3:1391

Ibn ‘Ulayyah narrated to us, from Yahya ibn Abi Ishaq, who said: I prayed the Maghrib prayer while al-Hakam ibn Ayyub was our Imam, and Abu Mulayh was beside Ibn Usamah. I heard him reciting the Opening of the Book (al-Fatihah). When the Imam finished with the taslim, I said to Abu Mulayh, "Do you recite behind the Imam while he is reciting?" He said, "I heard something." I said, "Yes."