Musnad Ahmad 30:1208

Wahb ibn Jarir narrated to us, he said: My father narrated to us, he said: I heard al-Nu’man narrating from al-Zuhri, from Humayd ibn ‘Abd al-Rahman, from Abu Hurayrah, that he said: "The Prophet of Allah, may Allah bless him and grant him peace, went out one day to seek rain. He prayed two rak'ahs with us without adhan or iqamah. Then he delivered a sermon to us and supplicated to Allah, the Almighty and Majestic, and he turned his face toward the qiblah, raising his hands. Then he turned his cloak inside out, placing the right side over the left, and the left side over the right."