I heard the Messenger of Allah say, "Whoever touches his private part must perform ablution."
سمعت رسول الله يقول: من مس فرجه فليتوضأ.
No references are available.
Ibn Majah narrated it (481) through two paths from Haytham bin Humayd, who said, "Ala bin Harith narrated to us, from Makhul, from Anbasah bin Abu Sufyan, from Umm Habiba," and he mentioned it. Its isnad is sahih.There is disagreement over whether Makhul heard from Anbasah. Ibn Main, Bukhari, Abu Hatim, and Nasai said, "He did not hear from him," while Duhaym of Damascus (d. 245 AH) disagreed with them and affirmed that Makhul did hear from Anbasah. Duhaym was one of the great memorizers of the nation, relied upon for validating and criticizing the sheikhs of Syria.Khallal said, "Ahmad graded the hadith of Umm Habiba as sahih." Abu Zura and Hakim also graded it sahih, and Ibn Sakan said, "I know of no defect in it," as Hafiz mentioned in Talkhis.This means that these scholars affirmed that Makhul heard from Anbasah, and therefore they graded this hadith as sahih. It is well known that when there is disagreement over whether a hearing took place, the one who affirms it takes precedence over the one who denies it.Similar in meaning is what has been narrated from Jabir bin Abdullah and Abu Ayub Ansari, though both of their isnads contain weakness.