حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ، وَعُثْمَانَ بْنَ عَفَّانَ، وَعَائِشَةَ، زَوْجَ النَّبِيِّ صلى الله عليه وسلم كَانُوا يَقُولُونَ إِذَا مَسَّ الْخِتَانُ الْخِتَانَ فَقَدْ وَجَبَ الْغُسْلُ ‏.‏

Yahya related to me from Malik from Ibn Shihab from Said ibn al-Musayyab that Umar ibn al-Khattab and Uthman ibn Affan and A'isha, thewife of the Prophet, may Allah bless him and grant him peace, used tosay, "When the circumcised part touches the circumcised part, ghusl isobligatory." Translation Not Available

Book Ref: Muwatta Imam Malik Book 2 Hadith 103
Web Ref:  Muwatta Imam Malik Book 2 Hadith 73