The Book of Purification (Kitab Al-Taharah)
Muslim :: Book 2 : Hadith 576
This hadith is transmitted from A'mash by Abmad b. Yusuf al-Azdi, Mu'alla b. Asad, Abd al-Wahid, Sulaiman with the same chain of transmitters but for the words:" The other did not keep himself safe from being defiled by urine."