كتاب الرضاع
17
The Book of Suckling
(14)
Chapter: It is permissible for a wife to give her turn to a co-wife
(14)
باب جَوَازِ هِبَتِهَا نَوْبَتَهَا لِضَرَّتِهَا ‏‏

Hisham reported on the authority of his father that 'A'isha (Allah be pleased with her) used to say:

Does the woman not feel shy of offering herself to a man? Then Allah the Exalted and Glorious revealed this verse:" You may defer any of them you wish and take to yourself any you wish." I ('A'isha said): It seems to me that your Lord hastens to satisfy your desire.
وَحَدَّثَنَاهُ أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا عَبْدَةُ بْنُ سُلَيْمَانَ، عَنْ هِشَامٍ، عَنْ أَبِيهِ، عَنْ عَائِشَةَ، أَنَّهَا كَانَتْ تَقُولُ أَمَا تَسْتَحْيِي امْرَأَةٌ تَهَبُ نَفْسَهَا لِرَجُلٍ حَتَّى أَنْزَلَ اللَّهُ عَزَّ وَجَلَّ ‏{‏ تُرْجِي مَنْ تَشَاءُ مِنْهُنَّ وَتُؤْوِي إِلَيْكَ مَنْ تَشَاءُ‏}‏ فَقُلْتُ إِنَّ رَبَّكَ لَيُسَارِعُ لَكَ فِي هَوَاكَ.‏
Reference : Sahih Muslim 1464 b
In-book reference : Book 17, Hadith 65
USC-MSA web (English) reference : Book 8, Hadith 3454
  (deprecated numbering scheme)