Sahih Muslim 287c
The Book of Purification
The ruling on the urine of a nursing infant and how to wash it
Ubaidullah b. Abdullah b. 'Utba b. Mas'ud said: Umm Qais, daughter of Mihsan, was among the earliest female emigrants who took the oath of allegiance to the Messenger of Allah (ﷺ), and she was the sister of 'Ukkasha b. Mihsan, one amongst the sons of Asad b. Khuzaima. He (the narrator) said: She (Umm Qais) told me that she came to the Messenger of Allah (ﷺ) with her son and he had not attained the age of eating food. He (the narrator, 'Ubaidullah), said: She told me that her son passed urine in the lap of the Messenger of Allah (ﷺ). The Messenger of Allah (ﷺ) sent for water and sprayed it over his garment (over that part which was contaminated with the urine of the child) and he did not wash it thoroughly.