It was narrated that ‘Abeedah said:
When `Ali killed the people of an-Nahrawan he said: Look for him. And they found him in a ditch lying beneath the slain. They brought him out and ‘Ali (رضي الله عنه) came to his companions and said: If you could exercise restraint, I would have told you what Allah promised on the lips of Muhammad to those who kill them. I said: Did you hear that from the Messenger of Allah (ﷺ)? He said: Yes, by the Lord of the Ka`bah.