Sahih Bukhari
Judgments (Ahkaam)
Volume: 009 / Book Number: 089 / Hadith Number: 279
Narrated Sahl:
(the brother of Bani Sa'ida) A man from the Ansar came to the Prophet and said, "If a man finds another man sleeping with his wife, should he kill him?" That man and his wife then did Lian in the mosque while I was present.