Musannaf Ibn Abi Shayba 35:78

Abu al-Ahwas narrated to us, from Simak, from Qabus ibn al-Mukhariq, from Lubaba bint al-Harith, who said: Al-Husayn ibn Ali urinated upon the Prophet, may Allah bless him and grant him peace, so I said: "Give me your garment and wear another." He said: "The urine of a male infant is merely sprinkled [with water], while the urine of a female infant is washed."