ENOfficial
Narrated Umm Salamah, Ummul Mu'minin: Al-Hasan reported on the authority of his mother that she was Umm Salamah pouring water on the urine of the male child until the age when he did not eat food. When he began to eat food, she would wash (his urine). And she would wash the urine of the female child.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا عَبْدُ اللَّهِ بْنُ عَمْرِو بْنِ أَبِي الْحَجَّاجِ أَبُو مَعْمَرٍ، حَدَّثَنَا عَبْدُ الْوَارِثِ، عَنْ يُونُسَ، عَنِ الْحَسَنِ، عَنْ أُمِّهِ، أَنَّهَا أَبْصَرَتْ أُمَّ سَلَمَةَ تَصُبُّ الْمَاءَ عَلَى بَوْلِ الْغُلاَمِ مَا لَمْ يَطْعَمْ فَإِذَا طَعِمَ غَسَلَتْهُ وَكَانَتْ تَغْسِلُ بَوْلَ الْجَارِيَةِ .
sunnah.com