Qabus bin al-Mukhariq (may Allah have mercy on him) narrated from his father, from Umm al-Fadl (may Allah be pleased with her), who said: I said to the Prophet (peace and blessings be upon him): "I saw in a dream as if a part of you was in my house." He (peace and blessings be upon him) said: "It is good. Fatimah will give birth to a son; you will nurse him in your house." So she gave birth to Hasan, and he lived in my house. I brought him to the Messenger of Allah (peace and blessings be upon him), and he urinated on him (peace and blessings be upon him). I said: "O Messenger of Allah, take off this garment so that I may wash it." He (peace and blessings be upon him) said: "The urine of girls is washed, and the urine of a boy is not washed."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 21504