It was narrated from abu Hurairah that the Messenger of Allah said:

"No one who commits Zina (an immoral sexual act) is a believer at the moment when he is committing Zina; no one who steals is a believer at the moment when he is stealing; no one who drinks wine is a believer at the moment when he is drinking it; and no robber is a believer at the moment when he is robbing and the people are looking on.