وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ هِشَامِ بْنِ عُرْوَةَ، عَنْ أَبِيهِ، أَنَّهُ كَانَ يَقُولُ مَنْ مَسَّ ذَكَرَهُ فَقَدْ وَجَبَ عَلَيْهِ الْوُضُوءُ ‏.‏

Yahya related to me from Malik from Hisham ibn Urwa that hisfather used to say, "If any of you touches his penis he has to dowudu." Translation Not Available

Book Ref: Muwatta Imam Malik Book 2 Hadith 93
Web Ref:  Muwatta Imam Malik Book 2 Hadith 63