Abu Dawud Book 1, Hadith Number 23.

Chapter : Urinating while one is standing.

Narated By Hudhaifah : The Apostle of Allah (PBUH) came to a midden of some people and urinated while standing. He then asked for water and wiped his shoes.

Abu Dawud said: Musaddad, a narator, reported: I went far away from him. He then called me and I reached just near his heals.