Abu Dawud Book 27, Hadith Number 4082.

Chapter : Upto what extent one should wear the lower garment.

Narated By Abu Sa’id al-Khudri : AbdurRahman said: I asked Abu Sa’id al-Khudri about wearing lower garment. He said: You have come to the man who knows it very well. The Apostle of Allah (PBUH) said: The way for a believer to wear a lower garment is to have it halfway down his legs and he is guilty of no sin if it comes halfway between that and the ankles, but what comes lower than the ankles is in Hell. On the day of Resurrection. Allah will not look at him who trails his lower garment conceitedly.