Sunan Abi Dawud 4093
سنن أبي داود#4093SahihNarrated 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 (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
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Muhyi Al-Din Abdul HamidSahih
Zubair Ali ZaiIsnaad Sahih
In-book reference: 34:74