Language:
كتاب الطلاق
68
Divorce
(7)
Chapter: Whoever said to his wife: "You are Haram for me."
(7)
باب مَنْ قَالَ لاِمْرَأَتِهِ أَنْتِ عَلَىَّ حَرَامٌ
Sahih al-Bukhari 5264
Nafi' said:
When Ibn 'Umar was asked about person who had given three divorces, he said, "Would that you gave one or two divorces, for the Prophet (ﷺ) ordered me to do so. If you give three divorces then she cannot be lawful for you until she has married another husband (and is divorced by him)."
وَقَالَ اللَّيْثُ عَنْ نَافِعٍ، كَانَ ابْنُ عُمَرَ إِذَا سُئِلَ عَمَّنْ طَلَّقَ ثَلاَثًا قَالَ لَوْ طَلَّقْتَ مَرَّةً أَوْ مَرَّتَيْنِ فَإِنَّ النَّبِيَّ صلى الله عليه وسلم أَمَرَنِي بِهَذَا، فَإِنْ طَلَّقْتَهَا ثَلاَثًا حَرُمَتْ حَتَّى تَنْكِحَ زَوْجًا غَيْرَكَ‏.‏
Reference : Sahih al-Bukhari 5264
In-book reference : Book 68, Hadith 14
USC-MSA web (English) reference : Vol. 1, Book 63, Hadith 189
  (deprecated numbering scheme)