Musnad Ahmad 31:529

Ali ibn Ishaq narrated to us, Abdullah informed us, Ibn Lahi'ah informed us, from Habban ibn Wasi', from his father, from Abu Sa'id al-Khudri, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "If one of you prays in a single garment, let him place its two ends over his shoulders."