عن إبن شهاب قال وكان الرجل إذا أسلم اُمِر بالاختتان وإن كان كبيراً
الأدب المفرد للبخاري كتاب الختان
From Ibn Shihab who said: A man, if he became Muslim, would be ordered to have himself circumcised, even if he was grown up.
Al-Bukhari, Al-adab Al-mufrad [Exemplary Manners], The book of circumcision
