Musannaf Ibn Abi Shayba 3:2831

Abu Bakr narrated to us, he said: Ghundar narrated to us, from Shu'bah, from Simak bin Harb, he said: I said to him: "How did al-Nu'man deliver the sermon?" He said: "He would gesture with his hand." He said: "And al-Dahhak bin Qays, when he delivered a sermon, would close his hand over his mouth."