Sayyiduna Hasan (may Allah be pleased with him) narrates from his mother that she saw Sayyidah Umm Salamah (may Allah be pleased with her): she would sprinkle water over the urine of a nursing baby boy, and when he started eating food she would wash it, and she used to wash the urine of a baby girl.
The narrated hadiths on the difference between the urine of a baby boy and a baby girl in this chapter become strong when combined with one another. It seems they were not established in the view of Imam al-Shafi'i (may Allah have mercy on him) when he said: "No difference between the urine of a boy and a girl is clear to me from the established Sunnah." Al-Bukhari and Muslim held a similar view, since they did not include any of them in their two books, except that al-Bukhari considered the hadith of Abu al-Samh good and judged Hisham correct in narrating the hadith of Ali as marfu'. Along with that, the practice of Umm Salamah (may Allah be pleased with her) is authentically reported from her, in addition to the established hadiths mentioned earlier on sprinkling over a baby boy's urine.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4163