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 ﷺ 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. (Using translation from Abū Dāʾūd 4093)
سَمِعْتُ رَسُولَ اللهِ ﷺ يَقُولُ إِزْرَةُ الْمُؤْمِنِ إِلَى أَنْصَافِ السَّاقَيْنِ لَا جُنَاحَ أَوْ لَا حَرَجَ عَلَيْهِ فِيمَا بَيْنَهُ وَبَيْنَ الْكَعْبَيْنِ مَا كَانَ أَسْفَلَ مِنْ ذَلِكَ فَهُوَ فِي النَّارِ لَا يَنْظُرُ اللهُ إِلَى مَنْ جَرَّ إِزَارَهُ بَطَرًا