Language:
كتاب النكاح
67  
Wedlock, Marriage (Nikaah)
(37)
Chapter: Whoever said, "A marriage is not valid except through the Wali."
(36)
بَابُ مَنْ قَالَ لاَ نِكَاحَ إِلاَّ بِوَلِيٍّ
Sahih al-Bukhari 5130

Narrated Al-Hasan:

concerning the Verse: 'Do not prevent them' (2.232) Ma'qil bin Yasar told me that it was revealed in his connection. He said, "I married my sister to a man and he divorced her, and when her days of 'Idda (three menstrual periods) were over, the man came again and asked for her hand, but I said to him, 'I married her to you and made her your bed (your wife) and favored you with her, but you divorced her. Now you come to ask for her hand again? No, by Allah, she will never go back to you (again)!' That man was not a bad man and his wife wanted to go back to him. So Allah revealed this Verse: 'Do not prevent them.' (2.232) So I said, 'Now I will do it (let her go back to him), O Allah's Messenger (ﷺ)."So he married her to him again.

حَدَّثَنَا أَحْمَدُ بْنُ أَبِي عَمْرٍو، قَالَ حَدَّثَنِي أَبِي قَالَ، حَدَّثَنِي إِبْرَاهِيمُ، عَنْ يُونُسَ، عَنِ الْحَسَنِ، ‏{‏فَلاَ تَعْضُلُوهُنَّ‏}‏ قَالَ حَدَّثَنِي مَعْقِلُ بْنُ يَسَارٍ، أَنَّهَا نَزَلَتْ فِيهِ قَالَ زَوَّجْتُ أُخْتًا لِي مِنْ رَجُلٍ فَطَلَّقَهَا، حَتَّى إِذَا انْقَضَتْ عِدَّتُهَا جَاءَ يَخْطُبُهَا، فَقُلْتُ لَهُ زَوَّجْتُكَ وَفَرَشْتُكَ وَأَكْرَمْتُكَ، فَطَلَّقْتَهَا، ثُمَّ جِئْتَ تَخْطُبُهَا، لاَ وَاللَّهِ لاَ تَعُودُ إِلَيْكَ أَبَدًا، وَكَانَ رَجُلاً لاَ بَأْسَ بِهِ وَكَانَتِ الْمَرْأَةُ تُرِيدُ أَنَّ تَرْجِعَ إِلَيْهِ فَأَنْزَلَ اللَّهُ هَذِهِ الآيَةَ ‏{‏فَلاَ تَعْضُلُوهُنَّ‏}‏ فَقُلْتُ الآنَ أَفْعَلُ يَا رَسُولَ اللَّهِ‏.‏ قَالَ فَزَوَّجَهَا إِيَّاهُ‏.‏
Reference : Sahih al-Bukhari 5130
In-book reference : Book 67, Hadith 66
USC-MSA web (English) reference : Vol. 7, Book 62, Hadith 61
  (deprecated numbering scheme)