كتاب الطهارة
1  
The Book of Purification
(167)
Chapter: The Junub Person Performing Wudu' And Washing His Penis When He Wants To Sleep
(167)
باب وُضُوءِ الْجُنُبِ وَغَسْلِ ذَكَرِهِ إِذَا أَرَادَ أَنْ يَنَامَ
Sunan an-Nasa'i 260
It was narrated that Ibn 'Umar said:
"Umar mentioned to the Messenger of Allah (ﷺ) that he became Junub at night, and the Messenger of Allah (ﷺ) said: 'Perform Wudu' and wash you penis, then sleep.'"
أَخْبَرَنَا قُتَيْبَةُ، عَنْ مَالِكٍ، عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ، عَنِ ابْنِ عُمَرَ، قَالَ ذَكَرَ عُمَرُ لِرَسُولِ اللَّهِ صلى الله عليه وسلم أَنَّهُ تُصِيبُهُ الْجَنَابَةُ مِنَ اللَّيْلِ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏ "‏ تَوَضَّأْ وَاغْسِلْ ذَكَرَكَ ثُمَّ نَمْ ‏"‏ ‏.‏
Grade: Sahih (Darussalam)
Reference : Sunan an-Nasa'i 260
In-book reference : Book 1, Hadith 261
English translation : Vol. 1, Book 1, Hadith 261