The Book of Ghusl and Tayammum
4/30. Chapter:
Wudu' After Touching One's Penis
Sunan an-Nasai
أَخْبَرَنَا قُتَيْبَةُ، عَنْ سُفْيَانَ، عَنْ عَبْدِ اللَّهِ، - يَعْنِي ابْنَ أَبِي بَكْرٍ - قَالَ عَلَى أَثَرِهِ قَالَ أَبُو عَبْدِ الرَّحْمَنِ وَلَمْ أُتْقِنْهُ عَنْ عُرْوَةَ، عَنْ بُسْرَةَ، قَالَتْ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " مَنْ مَسَّ فَرْجَهُ فَلْيَتَوَضَّأْ " .
It was narrated that Busrah said: "The Messenger of Allah (ﷺ) said: 'Whoever touches his private part, let him perform Wudu'.'"
Reference : Sunan an-Nasa'i 444In-book reference : Book 4, Hadith 50English translation : Vol. 1, Book 4, Hadith 445