I brought a son of mine, who had not yet started eating solid food, to the Messenger of Allah ﷺ, and he urinated on him. He called for water and sprinkled it over the spot.
حدثنا أبو بكر بن أبي شيبة ومحمد بن الصباح قالا حدثنا سفيان بن عيينة عن الزهري عن عبيد الله بن عبد الله
دخلت بابن لي على رسول الله ﷺ لم يأكل الطعام فبال عليه فدعا بماء فرش عليه
Bukhari transmitted it in the Wudu chapter, section on the urine of young children, no. 223, and Muslim in the Purification chapter, section on the ruling on the urine of a nursing infant and how it is washed, no. 287, from the hadith of Zuhri, through this same chain.