Whoever tells you that the Messenger of Allah ﷺ urinated standing up, do not believe him. I saw him urinating sitting down.
حدثنا أبو بكر بن أبي شيبة وسويد بن سعيد وإسمعيل بن موسى السدي قالوا حدثنا شريك عن المقدام بن شريح بن هانئ عن أبيه
من حدثك أن رسول الله ﷺ بال قائما فلا تصدقه أنا رأيته يبول قاعدا
[Hasan] Reported by Tirmidhi, in the Book of Purification, chapter on the prohibition of urinating while standing, from the hadith of Sharik, and Israel and others followed him in narrating it (Sunan al-Kubra by Bayhaqi: 1/101, 102). H: 12