كتاب الحيض
3  
The Book of Menstruation
(7)
Chapter: Women are obliged to perform ghusl if they emit fluid
(7)
باب وُجُوبِ الْغُسْلِ عَلَى الْمَرْأَةِ بِخُرُوجِ الْمَنِيِّ مِنْهَا ‏‏
Sahih Muslim 310

Anas b. Malik reported:

Umm Sulaim who was the grandmother of Ishaq came to the Messenger of Allah (ﷺ) in the presence of 'A'isha and said to him: Messenger of Allah, in case or woman sees what a man sees in dream and she experiences in dream what a man experiences (i. e. experiences orgasm)? Upon this 'A'isha remarked: O Umm Sulaim, you brought humiliation to women;may your right hand be covered with dust. He (the Holy Prophet) said to 'A'isha: Let your hand be covered with dust, and (addressing Umm Sulaim) said: Well, O Umm Sulaim, she should take a bath if she sees that (i. e. she experiences orgasm in dream).
وَحَدَّثَنِي زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا عُمَرُ بْنُ يُونُسَ الْحَنَفِيُّ، حَدَّثَنَا عِكْرِمَةُ بْنُ عَمَّارٍ، قَالَ قَالَ إِسْحَاقُ بْنُ أَبِي طَلْحَةَ حَدَّثَنِي أَنَسُ بْنُ مَالِكٍ، قَالَ جَاءَتْ أُمُّ سُلَيْمٍ - وَهِيَ جَدَّةُ إِسْحَاقَ - إِلَى رَسُولِ اللَّهِ صلى الله عليه وسلم فَقَالَتْ لَهُ وَعَائِشَةُ عِنْدَهُ يَا رَسُولَ اللَّهِ الْمَرْأَةُ تَرَى مَا يَرَى الرَّجُلُ فِي الْمَنَامِ فَتَرَى مِنْ نَفْسِهَا مَا يَرَى الرَّجُلُ مِنْ نَفْسِهِ ‏.‏ فَقَالَتْ عَائِشَةُ يَا أُمَّ سُلَيْمٍ فَضَحْتِ النِّسَاءَ تَرِبَتْ يَمِينُكِ ‏.‏ فَقَالَ لِعَائِشَةَ ‏ "‏ بَلْ أَنْتِ فَتَرِبَتْ يَمِينُكِ نَعَمْ فَلْتَغْتَسِلْ يَا أُمَّ سُلَيْمٍ إِذَا رَأَتْ ذَاكِ ‏"‏ ‏.‏
Reference : Sahih Muslim 310
In-book reference : Book 3, Hadith 31
USC-MSA web (English) reference : Book 3, Hadith 607
  (deprecated numbering scheme)