The Messenger of Allah ﷺ forbade letting one's garment hang loose in prayer and forbade a man from covering his mouth.
حدثنا محمد بن العلاء وإبراهيم بن موسى عن ابن المبارك عن الحسن بن ذكوان عن سليمان الأحول عن عطاء قال إبراهيم
أن رسول الله ﷺ نهى عن السدل في الصلاة وأن يغطي الرجل فاه
[Its chain is daif]. Ibn Khuzayma, no. 772, 918, narrated it from the hadith of Abdullah bin Mubarak, with this wording, and Ibn Majah, no. 966, narrated it from the hadith of Hasan bin Zakwan, with this wording, in abridged form.Hasan bin Zakwan is a mudallis, as mentioned earlier at no. 11, and I did not find an explicit statement that he heard it directly. Asal bin Sufyan is daif, and Tirmidhi narrated it through his route, no. 378. There occurs in Mustadrak (1/253) a strange error, see Ithaf Mahra (15/375).