Sahih Bukhari Volume 1, Book 4, Hadith 223

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يُوسُفَ، قَالَ أَخْبَرَنَا مَالِكٌ، عَنِ ابْنِ شِهَابٍ، عَنْ عُبَيْدِ اللَّهِ بْنِ عَبْدِ اللَّهِ بْنِ عُتْبَةَ، عَنْ أُمِّ قَيْسٍ بِنْتِ مِحْصَنٍ، أَنَّهَا أَتَتْ بِابْنٍ لَهَا صَغِيرٍ، لَمْ يَأْكُلِ الطَّعَامَ إِلَى رَسُولِ اللَّهِ صلى الله عليه وسلم، فَأَجْلَسَهُ رَسُولُ اللَّهِ صلى الله عليه وسلم فِي حِجْرِهِ، فَبَالَ عَلَى ثَوْبِهِ، فَدَعَا بِمَاءٍ فَنَضَحَهُ وَلَمْ يَغْسِلْهُ‏

Narrated By Um Qais bint Mihsin : I brought my young son, who had not started eating (ordinary food) to Allah's Apostle who took him and made him sit in his lap. The child urinated on the garment of the Prophet, so he asked for water and poured it over the soiled (area) and did not wash it.