Language:
كتاب الصلاة
8  
Prayers (Salat)
(44)
Chapter: To give the judicial verdicts in the mosque and to perform the Al-Lian between men and women (husbands and wives) there
(44)
باب الْقَضَاءِ وَاللِّعَانِ فِي الْمَسْجِدِ بَيْنَ الرِّجَالِ وَالنِّسَاءِ
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.‏
Reference : Sahih al-Bukhari 423
In-book reference : Book 8, Hadith 73
USC-MSA web (English) reference : Vol. 1, Book 8, Hadith 415
  (deprecated numbering scheme)