Musannaf Ibn Abi Shayba 3:449

Abu Bakr narrated to us, he said: Affan narrated to us, he said: Sa’id ibn Zayd narrated to us, he said: Abu ‘Abd Allah [al-Shaqari] narrated to us, from Isma’il ibn Raja’ ibn Rabi’ah, from his father, who said: We were with Abu Sa’id al-Khudri during the illness in which he passed away. He said: Then he fainted. When he regained consciousness, we said to him: "The prayer, O Abu Sa’id!" He said: "Kaffan." Abu Bakr said: He meant "kaffan," meaning he gestured.