كتاب الطهارة
1  
The Book of Purification
(32)
Chapter: That It Is Disliked To Urinate In A Place Where One Bathes
(32)
باب كَرَاهِيَةِ الْبَوْلِ فِي الْمُسْتَحَمِّ ‏‏
Sunan an-Nasa'i 36
It was narrated from 'Abdullah bin Mughaffal that the Prophet (ﷺ) said:
"None of you should urinate in the place where he bathes, for most Waswas (devilish whispers) [1] come from that." [1] I.e., with regard to whether the urine has soiled his body or not.
أَخْبَرَنَا عَلِيُّ بْنُ حُجْرٍ، قَالَ أَنْبَأَنَا ابْنُ الْمُبَارَكِ، عَنْ مَعْمَرٍ، عَنِ الأَشْعَثِ بْنِ عَبْدِ اللَّهِ، عَنِ الْحَسَنِ، عَنْ عَبْدِ اللَّهِ بْنِ مُغَفَّلٍ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏ "‏ لاَ يَبُولَنَّ أَحَدُكُمْ فِي مُسْتَحَمِّهِ فَإِنَّ عَامَّةَ الْوَسْوَاسِ مِنْهُ ‏"‏ ‏.‏
Grade: Hasan (Darussalam)
Reference : Sunan an-Nasa'i 36
In-book reference : Book 1, Hadith 36
English translation : Vol. 1, Book 1, Hadith 36