Yahya related to me from Malik from al Ala ibn Abd ar-Rahman thathis father said, "I asked Abu Said al-Khudri about the lower garment.He said that he would inform me with knowledge and that he had heardthe Messenger of Allah, may Allah bless him and grant him peace, say,'The lower garment of the mumin should reach to the middle of hiscalves. There is no harm in what is between that and the ankles. Whatis lower than that is in the Fire. What is lower than that is in theFire. On the Day of Rising, Allah will not look at a person who trailshis lower garment in arrogance.' "
USC-MSA web (English) reference: Book 48, Hadith 12
Arabic reference: Book 48, Hadith 1666