Aishah reported that the Messenger of Allah ﷺ would have children brought to him so he could bless them and rub their palates with chewed dates. A child was once brought to him who urinated on him, so he called for water and poured it over the spot without washing it.
ﷺ: أن رسول الله ﷺ كان يؤتى بالصبيان فيبرك عليهم ويحنكهم فأتي بصبي فبال عليه، فدعا بماء فأتبعه بوله ولم يغسله.
Bukhari narrated it in the Aqiqah chapter (5468) through Yahya, and Muslim narrated it in the Purification chapter (286:101) through Abdullah bin Numayr, both of them from Hisham, from his father, from Ayesha, who related it. The wording given is Muslim's. Bukhari has only the second half, with the wording, "The Prophet ﷺ was brought a small boy for him to give tahnik, and the boy urinated on him, so he had water poured over it." Muslim likewise narrated only the first half of it in the Manners chapter (27:2147) with the same chain of transmission.