Language:
كتاب الطلاق
68  
Divorce
(35)
Chapter: The child is to be given to the lady (accused by her husband).
(35)
باب يَلْحَقُ الْوَلَدُ بِالْمُلاَعِنَةِ
Sahih al-Bukhari 5315

Narrated Ibn `Umar:

The Prophet (ﷺ) made a man and his wife carry out Lian, and the husband repudiated her child. So the Prophet got them separated (by divorce) and decided that the child belonged to the mother only.

حَدَّثَنَا يَحْيَى بْنُ بُكَيْرٍ، حَدَّثَنَا مَالِكٌ، قَالَ حَدَّثَنِي نَافِعٌ، عَنِ ابْنِ عُمَرَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم لاَعَنَ بَيْنَ رَجُلٍ وَامْرَأَتِهِ، فَانْتَفَى مِنْ وَلَدِهَا فَفَرَّقَ بَيْنَهُمَا، وَأَلْحَقَ الْوَلَدَ بِالْمَرْأَةِ‏.‏
Reference : Sahih al-Bukhari 5315
In-book reference : Book 68, Hadith 64
USC-MSA web (English) reference : Vol. 7, Book 63, Hadith 235
  (deprecated numbering scheme)