Sahih al-Bukhari 423
Narrated Sahl bin Sa`d:
A man said, "O Allah's Messenger (ﷺ)! 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 Li`an in the mosque 
(taking oaths, one accusing, and the other denying adultery).
حَدَّثَنَا يَحْيَى، قَالَ أَخْبَرَنَا عَبْدُ الرَّزَّاقِ، قَالَ أَخْبَرَنَا ابْنُ جُرَيْجٍ، قَالَ أَخْبَرَنِي ابْنُ شِهَابٍ، عَنْ سَهْلِ بْنِ سَعْدٍ، أَنَّ رَجُلاً، قَالَ يَا رَسُولَ اللَّهِ، أَرَأَيْتَ رَجُلاً وَجَدَ مَعَ امْرَأَتِهِ رَجُلاً أَيَقْتُلُهُ فَتَلاَعَنَا فِي الْمَسْجِدِ وَأَنَا شَاهِدٌ‏.‏