Musnad Abu Ya'la al-Mawsili 42:317

Zuhayr narrated to us, Ya'qub ibn Ibrahim narrated to us, my father narrated to us, from Salih, who said: Ibn Shihab said: Abu Umamah ibn Sahl narrated to me that he heard Abu Sa'id al-Khudri say: The Messenger of Allah (ﷺ) said: "While I was sleeping, I saw the people being presented to me, and upon them were shirts. Some of them reached the chest, and some of them reached less than that. And 'Umar ibn al-Khattab passed by, and upon him was a shirt that he was dragging." They said: "How did you interpret that, O Messenger of Allah?" He said: "The religion."