Musannaf Ibn Abi Shayba 24:139

Ibn ‘Uyaynah narrated to us, from Dawud ibn Shabur, from Mujahid, who said: We used to boast over the people regarding four: our jurist, our storyteller, our caller to prayer, and our reciter. Our jurist was Ibn ‘Abbas, our caller to prayer was Abu Mahdhurah, our storyteller was ‘Ubayd ibn ‘Umayr, and our reciter was ‘Abdullah ibn al-Sa’ib.