Abu Dawud Book 1, Hadith Number 375.

Chapter : How to clean the clothe smeared with the urine of a child.

Narated By Lubabah daughter of al-Harith : Al-Husayn ibn Ali was (sitting) in the lap of the Apostle of Allah (PBUH). He passed water on him. I said: Put on (another) clothe, and give me your wrapper to wash. He said: The urine of a female child should be washed (thoroughly) and the urine of a male child should be sprinkled over.