Sahih Bukhari
Prayers (Salat)
Volume: 001 / Book Number: 008 / Hadith Number: 415
Narrated Sahl bin Sa'd:
A man said, "O Allah's Apostle! If a man finds another man with his wife, (committing adultery) should the husband kill him?" Later on I saw them (the man and his wife) doing Lian in the mosque.