It was narrated that ‘Imran bin Husain and Abu Barzah said:“We went out with the Messenger of Allah (ﷺ) to attend a funeral, and he saw some people who had cast aside their upper sheets and were walking in their shirts only. The Messenger of Allah (ﷺ) said: ‘Are you adopting the practice of the days of ignorance?’ or; ‘Are you imitating the behavior of the days of ignorance? I was about to supplicate against you that you would return in a different form.’ So they put their sheets back on and never did that again.”

English translation · Sunan Ibn Majah