Sa’d bin Jubair said I asked Ibn ‘Umar A man accused his wife of adultery? He said “The Messenger of Allah(ﷺ) separated the brother and the sister of Banu Al ‘Ajilan (i.e., husband and wife). He said Allaah knows that one of you is a liar, will one of you repent? He repeated these words three times, but they refused. So he separated them from each other.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا أَحْمَدُ بْنُ مُحَمَّدِ بْنِ حَنْبَلٍ، حَدَّثَنَا إِسْمَاعِيلُ، حَدَّثَنَا أَيُّوبُ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، قَالَ قُلْتُ لاِبْنِ عُمَرَ رَجُلٌ قَذَفَ امْرَأَتَهُ . قَالَ فَرَّقَ رَسُولُ اللَّهِ صلى الله عليه وسلم بَيْنَ أَخَوَىْ بَنِي الْعَجْلاَنِ وَقَالَ " اللَّهُ يَعْلَمُ أَنَّ أَحَدَكُمَا كَاذِبٌ . فَهَلْ مِنْكُمَا تَائِبٌ " . يُرَدِّدُهَا ثَلاَثَ مَرَّاتٍ فَأَبَيَا فَفَرَّقَ بَيْنَهُمَا .
sunnah.com