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'." (DE)
English reference (DE): Vol. 1, Book 1, Hadith 260 (DE)
Arabic reference (DE): Book 1, Hadith 261 (DE)