ما رأى أحد رسول الله ﷺ يبول قائماً منذ أنزل عليه القرآن
السنن الكبرى للبيهقي
Nobody ever saw the Messenger of Allah (SAW) urinate standing up once the Quran had been sent down to him.
The Greater Compilation of Sunnah [Al-sunan Al-kubra] by Al-Bayhaqi
