«من مس ذكره فليتوضأ»
Whoever touches his private parts should perform ablution.
The chapter discusses this report alongside the Qur'anic wording «فِيهِ رِجَالٌ يُحِبُّونَ أَنْ يَتَطَهَّرُوا», considering how a rule of purity is related to the proposed additional cause of ritual impurity.
The point is not that all jurists agree on the final ruling; this is a disputed legal question. The student should distinguish establishing a new cause for loss of ablution from explaining an existing command concerning purification.