حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا أَبُو مُعَاوِيَةَ، عَنْ حَجَّاجٍ، عَنْ عَمْرِو بْنِ شُعَيْبٍ، عَنْ أَبِيهِ، عَنْ جَدِّهِ، قَالَ قَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ ‏"‏ إِذَا الْتَقَى الْخِتَانَانِ وَتَوَارَتِ الْحَشَفَةُ فَقَدْ وَجَبَ الْغُسْلُ ‏"‏ ‏.‏

It was narrated from 'Amr bin Shu'aib from his father, that his grandfather said: "The Messenger of Allah said: 'When the two circumcised parts meet, and (the tip of the penis) disappears, then bath is obligatory.'" Translation Not Available

Book Ref: Sunan Ibn Majah Book 1 Hadith 611
Web Ref:  Sunan Ibn Majah Vol 1 Book 1 Hadith 611