Musannaf Ibn Abi Shayba 3:4903

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Ibn Abi Dhi’b, from Shu’bah, the freed slave of Ibn Abbas, he said: I prayed beside Ibn Abbas, and I cracked my fingers. When I finished the prayer, he said: "May you have no mother! You crack your fingers while you are in the prayer?"