Sahih Bukhari Volume 7, Book 63, Hadith Number 227.

Narrated By Ibn ‘Abbas : Hilal bin Umaiyya accused his wife of illegal sexual intercourse and came to the Prophet to bear witness (against her), (taking the oath of Lian). The Prophet was saying, “Allah knows that either of you is a liar. Will anyone of you repent (to Allah)?” Then the lady got up and gave her witness.