Muwatta Malik 91
موطأ مالك#91SahihYahya related to me from Malik from Nafi that Abdullah ibn Umar used to say, "If you touch your penis you have to do wudu
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Salim al-HilaliMauquf Sahih
In-book reference: 2:60