A boy was brought to the Prophet ﷺ to do Tahnik for him, but the boy urinated on him, whereupon the Prophet had water poured on the place of urine.

أُتِيَ النَّبِيُّ ﷺ بِصَبِيٍّ يُحَنِّكُهُ فَبَالَ عَلَيْهِ فَأَتْبَعَهُ الْمَاءَ