Sunan Abi Dawud, Book 32, Hadith 4082 (USC-MSA) ⓘ

Narrated Abdur Rahman: 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 Messenger of Allah 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.

حَدَّثَنَا حَفْصُ بْنُ عُمَرَ، حَدَّثَنَا شُعْبَةُ، عَنِ الْعَلاَءِ بْنِ عَبْدِ الرَّحْمَنِ، عَنْ أَبِيهِ، قَالَ سَأَلْتُ أَبَا سَعِيدٍ الْخُدْرِيَّ عَنِ الإِزَارِ، فَقَالَ عَلَى الْخَبِيرِ سَقَطْتَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏ "‏ إِزْرَةُ الْمُسْلِمِ إِلَى نِصْفِ السَّاقِ وَلاَ حَرَجَ - أَوْ لاَ جُنَاحَ - فِيمَا بَيْنَهُ وَبَيْنَ الْكَعْبَيْنِ مَا كَانَ أَسْفَلَ مِنَ الْكَعْبَيْنِ فَهُوَ فِي النَّارِ مَنْ جَرَّ إِزَارَهُ بَطَرًا لَمْ يَنْظُرِ اللَّهُ إِلَيْهِ ‏" ‏ ‏.‏