Abu Dawud Book 1, Hadith Number 378.

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

Narated By Ali b. Abi Talib : The Prophet (PBUH) said: He narrated the tradition to the same effect, but he did not mention the words “until the age of eating.” This version adds: Qatadah said: This is valid until the time they do not eat food; when they begin to eat, their urine should be washed.