Sunan Abi Dawud, Hadith 2131

Narrated 'Aishah: The Messenger of Allah used to aske our permission on the day he had to stay with one of his wives (by turns) after the following Qur'anic verse was revealed: "You may distance those whom you like, and draw close to those whom you like" [33:51]. The narrator Mu'adhah said: I said to her: What did you say to the Messenger of Allah ? She said: I used to say: If had an option for that, I would not preferred anyone to myself.

حَدَّثَنَا يَحْيَى بْنُ مَعِينٍ، وَمُحَمَّدُ بْنُ عِيسَى، - الْمَعْنَى - قَالاَ حَدَّثَنَا عَبَّادُ بْنُ عَبَّادٍ، عَنْ عَاصِمٍ، عَنْ مُعَاذَةَ، 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 ‏}‏ قَالَتْ مُعَاذَةُ فَقُلْتُ لَهَا مَا كُنْتِ تَقُولِينَ لِرَسُولِ اللَّهِ صلى الله عليه وسلم قَالَتْ كُنْتُ أَقُولُ إِنْ كَانَ ذَلِكَ إِلَىَّ لَمْ أُوثِرْ أَحَدًا عَلَى نَفْسِي ‏.‏

sunnah.com

also referenced under: Hadith 2136 (DarusSalam)