سنن النسائي

It was narrated that Ya'la bin Umayyah said: "I went on a campaign with the Messenger of Allah (ﷺ) in the Army of Hardship, and this was the deed of which I was most sure. I had a hired man who fought with another person. One of them bit the finger of the other, who pulled his finger away and a front tooth fell out. He went to the Prophet (ﷺ) who considered the tooth to be in vain, and said: "Would he put his hand in your mouth for you to bite it?"