Sahih Muslim Book - 3, Hadith - 703

و حَدَّثَنَا مُحَمَّدُ بْنُ رَافِعٍ حَدَّثَنَا عَبْدُ الرَّزَّاقِ عَنْ ابْنِ جُرَيْجٍ أَخْبَرَنِي نَافِعٌ عَنْ ابْنِ عُمَرَ أَنَّ عُمَرَ اسْتَفْتَى النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَقَالَ هَلْ يَنَامُ أَحَدُنَا وَهُوَ جُنُبٌ قَالَ نَعَمْ لِيَتَوَضَّأْ ثُمَّ لِيَنَمْ حَتَّى يَغْتَسِلَ إِذَا شَاءَ.

It was narrated from Ibn 'Umar, that 'Umar consulted the Prophet (s.a.w) and said: "Can one of us go to sleep while he is Junub?" He said: "Yes. Let him perform Wudu' and then go to sleep, until he does Ghusl whenever he wishes."