Hadithcore
Sunan Abi Dawud, 379
sahih· Al-Albani

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.

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 ‏.‏

References2 variants
In-Book Reference
Book 1, Hadith 379
English Reference
Book 1, Hadith 379