Narrated Abu Huraira (Radi-Allahu 'anhu):

The Prophet (Sallallahu 'Alaihi Wa Sallam) said, "When an adulterer commits
illegal sexual intercourse, then he is not a believer at the time he is
doing it, and when a drinker of an alcoholic liquor drinks it, then he is
not a believer at the time of drinking it, and when a thief steals, then he
is not a believer at the time of stealing, and when a robber robs, and the
people look at him, then he is not a believer at the time of doing
robbery."

Bukhari Vol. 3 : No. 655