Sunan Abi Dawud
Hadith #643
Narrated AbuHurayrah: The Messenger of Allah (ﷺ) forbade trailing garments during prayer and that a man should cover his mouth. Abu Dawud said: This tradition has also been narrated by 'Isi on the authority of 'Ata' from Abu Hurairah: The Prophet (ﷺ) forbade trailing garments during prayer