Hudhayfah reported: The Prophet, peace and blessings be upon him, came to a waste area used by people and he urinated over it while standing. I brought him water for ablution and then left him to his privacy. The Prophet called me until I was behind him and he performed ablution, wiping over his leather socks.
Al-Tirmidhi said, “A concession was granted from some of the people of knowledge to urinate while standing.”
Source: Sunan al-Tirmidhī 13
Grade: Sahih (authentic) according to Al-Albani
عَنْ حُذَيْفَةَ أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَتَى سُبَاطَةَ قَوْمٍ فَبَالَ عَلَيْهَا قَائِمًا فَأَتَيْتُهُ بِوَضُوءٍ فَذَهَبْتُ لِأَتَأَخَّرَ عَنْهُ فَدَعَانِي حَتَّى كُنْتُ عِنْدَ عَقِبَيْهِ فَتَوَضَّأَ وَمَسَحَ عَلَى خُفَّيْهِ
قال الترمذي وَقَدْ رَخَّصَ قَوْمٌ مِنْ أَهْلِ الْعِلْمِ فِي الْبَوْلِ قَائِمًا
13 سنن الترمذي كتاب الطهارة باب الرخصة في ذلك
13 المحدث الألباني خلاصة حكم المحدث صحيح في صحيح الترمذي