Musnad Abu Ya'la al-Mawsili 214:4

Zuhayr narrated to us, Yahya ibn Abi Bukayr narrated to us, Isra'il narrated to us, from Simak, from Qabus ibn Abi al-Mukhariq, from Umm al-Fadl, who said: I saw as if there was a piece of the Messenger of Allah, may Allah bless him and grant him peace, in my house, and I was distressed by that. He said: "It is good, if Allah wills. Fatimah will give birth to a boy, and you will nurse him with the milk of your son, Qutham." She said: So she gave birth to Hasan, and she gave him to me, and I nursed him. Then I brought him and sat him in his lap, and he urinated on him. I struck him between his shoulders, and he said: "Be gentle, may Allah set you right—or may Allah have mercy on you—you have hurt my son." She said: I said, "Take off your lower garment and wear another garment until I wash it." He said: "The urine of a female infant is washed, and the urine of a male infant is sprinkled."