Sayyiduna Hudhayfah (may Allah be pleased with him) said that the Prophet (peace and blessings be upon him) stood at the rubbish heap of some people, and he (peace and blessings be upon him) urinated while standing. I moved away from him (peace and blessings be upon him), and he (peace and blessings be upon him) said: "Come close." So I came close; then he (peace and blessings be upon him) performed ablution and wiped over his leather socks.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 486
Sayyiduna Hudhayfah bin al-Yaman (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) and I were walking together, and he (peace and blessings be upon him) came behind the rubbish heap of some people and urinated in the way that one of you stands. The narrator said: I moved back, and he (peace and blessings be upon him) signalled to me, so I stood behind him (peace and blessings be upon him) until he (peace and blessings be upon him) had finished.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 487
It is narrated from Sayyiduna al-Mughirah bin Shu'bah (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) came to the rubbish heap of some people, and he (peace and blessings be upon him) urinated while standing. I met Mansur and asked him about it, and he narrated to me, from Abu Wa'il, the hadith of Sayyiduna Hudhayfah (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) came to the rubbish heap of some people and he (peace and blessings be upon him) urinated while standing.
Asim bin Bahdalah and Hammad bin Abi Sulayman narrated it this way, from Abu Wa'il from al-Mughirah, but the correct version is what Mansur and al-A'mash narrated from Abu Wa'il from Hudhayfah; Abu Isa al-Tirmidhi and a group of the hadith masters said so. A hadith has been narrated about the reason for his (peace and blessings be upon him) urinating while standing, the like of which is not established.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 488
It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) urinated while standing because of a wound that he (peace and blessings be upon him) had in his knees.
(b) Imam Ahmad (may Allah have mercy on him) said: One view is that the Arabs used to urinate standing to seek a cure for back pain, so it is possible that he (peace and blessings be upon him) also had this pain. Imam al-Shafi'i (may Allah have mercy on him) has given the same meaning. Another view is that he (peace and blessings be upon him) did so because there was no place there to sit. And Allah knows best.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 489