She saw Umm Salama pouring water over the urine of a baby boy as long as he had not yet started eating solid food, but once he began eating she would wash it. As for the urine of a baby girl, she would wash it.
حدثنا عبد الله بن عمرو بن أبي الحجاج أبو معمر حدثنا عبد الوارث عن يونس
أنها أبصرت أم سلمة تصب الماء على بول الغلام ما لم يطعم فإذا طعم غسلته وكانت تغسل بول الجارية
[Its isnad is daif]. Bayhaqi 2/416 reported it from the hadith of Abu Dawud through this route, and said, "Sahih." Al-Hafiz graded it sahih in Talkhis Habir 1/38, and the hadith has very many corroborating narrations.Hasan Basri is a mudallis, and he narrated using "an" (indicating possible concealment in the chain).