An-Nur · 24:2

2. The unmarried fornicating man and woman - flog each one of them with a hundred lashes, and no softness or mercy should affect you, whereby you do not establish the fixed punishment upon them or you make it lighter for them, if you believe in Allah and the Last Day. And a group of believers should be present when the fixed punishment is being executed on them, to go to the limit of publicising their crime, and to deter them and others.