Sahih Muslim Book - 3, Hadith - 705

حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ حَدَّثَنَا لَيْثٌ عَنْ مُعَاوِيَةَ بْنِ صَالِحٍ عَنْ عَبْدِ اللَّهِ بْنِ أَبِي قَيْسٍ قَالَ سَأَلْتُ عَائِشَةَ عَنْ وِتْرِ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ 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 الْأَمْرِ سَعَةً.

It was narrated that 'Abdullah bin Abi Qais said: "I asked 'Aishah about the Witr of the Messenger of Allah (s.a.w)" - and he mentioned the Hadith. I said: "What did he do in the case of Janabah? Did he perform Ghusl before he slept, or sleep before he performed Ghusl?" She said: "He would do both. Sometimes he performed Ghusl and then slept, and sometimes he would perform Wudu' and sleep." I said: "Praise be to Allah Who has made the matter flexible."