ENOfficial
It was narrated that Ibn 'Umar said: "The Messenger of Allah (ﷺ) conducted the procedure of Li'an between a man and his wife, and he separated them and attributed the child to his mother."
Source: sunnah.com
Other translations
Arabic
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا مَالِكٌ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، قَالَ لاَعَنَ رَسُولُ اللَّهِ صلى الله عليه وسلم بَيْنَ رَجُلٍ وَامْرَأَتِهِ وَفَرَّقَ بَيْنَهُمَا وَأَلْحَقَ الْوَلَدَ بِالأُمِّ .
sunnah.com