It is narrated from Sayyidah Umm Qays bint Mihsan (may Allah be pleased with her) that she came with a son of hers who did not yet eat food, and he urinated on the Messenger of Allah (peace and blessings be upon him), so he (peace and blessings be upon him) called for water and sprinkled it over it.
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 21898