(31) باب حُكْمِ بَوْلِ الطِّفْلِ الرَّضِيعِ وَكَيْفِيَّةِ غَسْلِهِ
Umm Qais daughter of Mihsan reported that she came to the Messenger of Allah (ﷺ) with her child. who was not yet weaned, and she placed him in his lap; and he urinated in his (Holy Prophet's) lap. He (the Holy Prophet) did nothing more than spraying water over it.
Reference: Sahih Muslim 287a
In-book reference: Book 2, Hadith 131
USC-MSA web (English) reference(deprecated numbering scheme): Book 2, Hadith 563