Sahih al-Bukhari 5468
Sahih al-Bukhari · Book 71: Sacrifice on Occasion of Birth (`Aqiqa) · The naming of a newly born child, Al-'Al-'Aqiqa and its Tahnik
Narrated `Aisha:
حَدَّثَنَا مُسَدَّدٌ ، حَدَّثَنَا يَحْيَى ، عَنْ هِشَامٍ ، عَنْ أَبِيهِ ، عَنْ عَائِشَةَ ـ رضى الله عنها ـ قَالَتْ أُتِيَ النَّبِيُّ صلى الله عليه وسلم بِصَبِيٍّ يُحَنِّكُهُ، فَبَالَ عَلَيْهِ، فَأَتْبَعَهُ الْمَاءَ.
A boy was brought to the Prophet (ﷺ) to do Tahnik for him, but the boy urinated on him, whereupon the Prophet had water poured on the place of urine.