كتاب الطلاق
18  
The Book of Divorce
(4)
Chapter: Giving one's wife the choice does not count as a divorce, unless it is intended as such
(4)
باب بَيَانِ أَنَّ تَخْيِيرَ امْرَأَتِهِ لاَ يَكُونُ طَلاَقًا إِلاَّ بِالنِّيَّةِ ‏‏
Sahih Muslim 1476 a

'A'isha (Allah be pleased with her) reported that Allah's Messenger (ﷺ) sought our permission when he had a (turn to spend) a day with (one of his wives) amongst us (whereas he wanted to visit his other wives too). It was after this that this verse was revealed:

" Thou mayest put off whom thou pleasest of them, and take for thee whom thou pleasest" (xxxiii. 5). Mu'adha said to her: What did you say to Allah's Messenger (ﷺ) when he sought your permission? She said: I used to say: If it had the option in this I would not have (allowed anyone) to have precedence over me.
حَدَّثَنَا سُرَيْجُ بْنُ يُونُسَ، حَدَّثَنَا عَبَّادُ بْنُ عَبَّادٍ، عَنْ عَاصِمٍ، عَنْ مُعَاذَةَ الْعَدَوِيَّةِ، عَنْ عَائِشَةَ، قَالَتْ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يَسْتَأْذِنُنَا إِذَا كَانَ فِي يَوْمِ الْمَرْأَةِ مِنَّا بَعْدَ مَا نَزَلَتْ ‏{‏ تُرْجِي مَنْ تَشَاءُ مِنْهُنَّ وَتُؤْوِي إِلَيْكَ مَنْ تَشَاءُ‏}‏ فَقَالَتْ لَهَا مُعَاذَةُ فَمَا كُنْتِ تَقُولِينَ لِرَسُولِ اللَّهِ صلى الله عليه وسلم إِذَا اسْتَأْذَنَكِ قَالَتْ كُنْتُ أَقُولُ إِنْ كَانَ ذَاكَ إِلَىَّ لَمْ أُوثِرْ أَحَدًا عَلَى نَفْسِي ‏.‏
Reference : Sahih Muslim 1476a
In-book reference : Book 18, Hadith 31
USC-MSA web (English) reference : Book 9, Hadith 3499
  (deprecated numbering scheme)