I came to the Prophet ﷺ with a son of mine who had not yet started eating solid food, and he urinated on him. The Prophet ﷺ called for water and sprinkled it over the spot.
حدثنا سفيان بن عيينة عن الزهري عن عبيد الله
دخلت على النبي ﷺ بابن لي لم يطعم فبال عليه فدعا بماء فرشه عليه
Its isnad is sahih. Ubaydullah is Ibn Abdullah bin Utba bin Masud, the trustworthy, precise jurist.The hadith was narrated by Bukhari 1/326 no. 223 in wudu, Muslim 1/238 no. 278, Abu Dawud 1/102 no. 374, Tirmidhi 1/105 no. 71, Nasai 1/157 no. 302, Darimi 1/206 no. 741, Ibn Majah 1/174 no. 524, and Ibn Khuzayma 1/144 no. 285, all of them in the chapter on purification.