Sunan an-Nasa'i 3477
سنن النسائي#3477Sahihأَخْبَرَنَا 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 .
It was narrated that Ibn 'Umar said:"The Messenger of Allah conducted the procedure of Li'an between a man and his wife, and he separated them and attributed the child to his mother
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih - Agreed Upon
In-book reference: 27:89