Sunan an-Nasa'i, Book 1, Hadith 261 (In-Book) ⓘ
It was narrated from 'Abdullah bin 'Umar that 'Umar said: "O Messenger of Allah! May any one of us sleep while he is Junub?" He said: "When he performs Wudu'."
أَخْبَرَنَا عُبَيْدُ اللَّهِ بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا يَحْيَى، عَنْ عُبَيْدِ اللَّهِ، قَالَ أَخْبَرَنِي نَافِعٌ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ عُمَرَ، قَالَ يَا رَسُولَ اللَّهِ أَيَنَامُ أَحَدُنَا وَهُوَ جُنُبٌ قَالَ " إِذَا تَوَضَّأَ " .
also referenced under: Volume 1, Book 1, Hadith 260 (DarusSalam)