The Book of Invoking Curses
وَحَدَّثَنِي أَبُو الرَّبِيعِ الزَّهْرَانِيُّ، حَدَّثَنَا حَمَّادٌ، عَنْ أَيُّوبَ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، عَنِ ابْنِ عُمَرَ، قَالَ فَرَّقَ رَسُولُ اللَّهِ صلى الله عليه وسلم بَيْنَ أَخَوَىْ بَنِي الْعَجْلاَنِ وَقَالَ " اللَّهُ يَعْلَمُ أَنَّ أَحَدَكُمَا كَاذِبٌ فَهَلْ مِنْكُمَا تَائِبٌ " .Ibn 'Umar (Allah be pleased with them) said that Allah's Messenger (ﷺ) effected separation between the two members of Banu al-'Ajlan, and said:Allah knows that one of you is a liar. Is there one to repent among you?
From Sahih Muslim, whose reports the scholars accept as authentic.