كتاب الحيض
3  
The Book of Menstruation
(6)
Chapter: It is permissible for one who is junub to sleep, but it is recommended for him to perform wudu’, and wash his private parts if he wants to eat, drink, sleep, or have intercourse
(6)
باب جَوَازِ نَوْمِ الْجُنُبِ وَاسْتِحْبَابِ الْوُضُوءِ لَهُ وَغَسْلِ الْفَرْجِ إِذَا أَرَادَ أَنْ يَأْكُلَ أَوْ يَشْرَبَ أَوْ يَنَامَ أَوْ يُجَامِعَل
Sahih Muslim 307 a

'Abdullah b. Abu'l-Qais reported:

I asked 'A'isha about the Witr (prayer) of the Messenger of Allah (ﷺ) and made mention of a hadith, then I said: What did he do after having sexual intercourse? Did he take a bath before going to sleep or did he sleep before taking a bath? She said: He did all these. Some- times he took a bath and then slept, and sometimes he performed ablution only and went to sleep. I (the narrator) said: Praise be to Allah Who has made things easy (for human beings).
حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا لَيْثٌ، عَنْ مُعَاوِيَةَ بْنِ صَالِحٍ، عَنْ عَبْدِ اللَّهِ بْنِ أَبِي قَيْسٍ، قَالَ سَأَلْتُ عَائِشَةَ عَنْ وِتْرِ، رَسُولِ اللَّهِ صلى الله عليه وسلم ‏.‏ فَذَكَرَ الْحَدِيثَ قُلْتُ كَيْفَ كَانَ يَصْنَعُ فِي الْجَنَابَةِ أَكَانَ يَغْتَسِلُ قَبْلَ أَنْ يَنَامَ أَمْ يَنَامُ قَبْلَ أَنْ يَغْتَسِلَ قَالَتْ كُلُّ ذَلِكَ قَدْ كَانَ يَفْعَلُ رُبَّمَا اغْتَسَلَ فَنَامَ وَرُبَّمَا تَوَضَّأَ فَنَامَ ‏.‏ قُلْتُ الْحَمْدُ لِلَّهِ الَّذِي جَعَلَ فِي الأَمْرِ سَعَةً ‏.‏
Reference : Sahih Muslim 307a
In-book reference : Book 3, Hadith 27
USC-MSA web (English) reference : Book 3, Hadith 603
  (deprecated numbering scheme)