Sahih Muslim 286b
Sahih Muslim · Book 2: The Book of Purification · The ruling on the urine of a nursing infant and how to wash it
A'isha reported:
وَ حَدَّثَنَا زُهَيْرُ بْنُ حَرْبٍ ، حَدَّثَنَا جَرِيرٌ ، عَنْ هِشَامٍ ، عَنْ أَبِيهِ ، عَنْ عَائِشَةَ ، قَالَتْ أُتِيَ رَسُولُ اللَّهِ صلى الله عليه وسلم بِصَبِيٍّ يَرْضَعُ فَبَالَ فِي حِجْرِهِ فَدَعَا بِمَاءٍ فَصَبَّهُ عَلَيْهِ .
A suckling babe was brought to the Messenger of Allah (way peace be upon him) and he urinated in his tap. He (the Holy Prophet) sent for water and poured it over.