Concerning exception for that
Abu Wail reported that Sayyidina Hudhayfah (RA) said that Allah's Messenger (SAW)
came to a midden of the people and passed urine standing. Then he brought water for
him to erform ablution and began to retreat but he called him until he was just behind
him. Then Prophet (SAW) performed ablution and wiped over his socks.
[Ahmed23301, 23405, Bukhari 224, Muslim 273, Nisai 26, 27, Abu Dawud 23, Ibn e Majah