Musnad Abu Ya'la al-Mawsili 129:34

Salih ibn Hatim ibn Wardan narrated to us, Mu'tamir ibn Sulayman narrated to us, he said: I heard Humayd al-Tawil narrating from Anas ibn Malik that the Prophet, peace and blessings of Allah be upon him, prayed behind Abu Bakr, may Allah be pleased with him, in one garment.