Musnad Abu Ya'la al-Mawsili 42:7

Zuhayr narrated to us, Sufyan narrated to us, al-Ala’ ibn Abd al-Rahman al-Juhani narrated to me, from his father, who said: I asked Abu Sa’id, "Did you hear anything from the Messenger of Allah (may Allah bless him and grant him peace) regarding the lower garment (izar)?" He said, "Yes." I said, "Narrate it to me." He said, "I heard him saying: 'The lower garment of the believer is up to the middle of his shins. There is no blame upon him in what is between that and the ankles. And whatever is below the ankles is in the Fire'—three times. 'Allah will not look at the one who drags his lower garment out of pride.'"