ENOfficial
It was narrated from 'Amr bin Shu'aib from his father, that his grandfather said: "The Messenger of Allah (ﷺ) said: 'When the two circumcised parts meet, and (the tip of the penis) disappears, then bath is obligatory.'"
Source: sunnah.com
Other translations
Arabic
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 " .
sunnah.com