Sahih Al Bukhari: 8.813:
Narrated Ibn `Abbas: When Ma'iz bin Malik came to the Prophet (in order to confess), the Prophet said to him, "Probably you have only kissed (the lady), or winked, or looked at her?" He said, "No, O Allah's Apostle!" The Prophet said, using no euphemism, "Did you have sexual intercourse with her?" The narrator added: At that, (i.e. after his confession) the Prophet ordered that he be stoned (to death).