Musnad Abu Ya'la al-Mawsili 42:117

Al-Hasan ibn ‘Umar ibn Shaqiq narrated to us, my father narrated to us, from Isma’il ibn Muslim, from al-A’mash, from ‘Atiyyah, from Abu Sa’id al-Khudri, who said: I entered upon the Prophet, may Allah bless him and grant him peace, while he was in the house of Umm Salamah, and he was praying in a single garment, wrapped in it.