Musannaf Ibn Abi Shayba 3:5959

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Sufyan narrated to us, from Hisham ibn Ishaq ibn ‘Abdullah ibn Kinana, from his father, who said: A commander from among the commanders sent me to Ibn ‘Abbas to ask him about the prayer for rain (istisqa’). Ibn ‘Abbas said: "What prevented him from asking me himself?" Then Ibn ‘Abbas said: The Messenger of Allah (peace and blessings of Allah be upon him) went out humble, in worn-out clothing, showing submissiveness, supplicating, and composed. He prayed two rak’ahs just as he prays on the ‘Eid, and he did not deliver a sermon like this sermon of yours.