Sayyiduna Umar (may Allah be pleased with him) said: Since I accepted Islam, I have never urinated standing.
Al-Bazzar recorded it, and its narrators are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الطهارة / 1015
Sayyiduna Sahl bin Sa'd (may Allah be pleased with him) narrates that he saw the Prophet (peace and blessings be upon him) urinating while standing.
Al-Tabarani recorded it in al-Mu'jam al-Awsat; its chain contains a narrator, Ibrahim bin Hammad bin Abi Hazim, and I have not seen anyone who mentions him.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الطهارة / 1016
Ibn Sirin narrates: Once Sayyiduna Sa'd bin Ubadah (may Allah be pleased with him) was urinating while standing; meanwhile he leaned (on something) and passed away. The jinn had killed him, and those jinn said: We have killed the chief of the Khazraj tribe, Sa'd bin Ubadah; we shot him with two arrows, which struck him straight in the heart.
Al-Tabarani recorded it in al-Mu'jam al-Kabir; Ibn Sirin did not live in the time of Sayyiduna Sa'd bin Ubadah (may Allah be pleased with him).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الطهارة / 1017
Qatadah narrates: Sayyiduna Sa'd bin Ubadah (may Allah be pleased with him) (once) urinated standing. When he came back he said: I feel something in my back. A short while later he passed away, and the jinn, lamenting him, said: We have killed the chief of the Khazraj tribe, Sayyiduna Sa'd bin Ubadah (may Allah be pleased with him); we shot him with an arrow, which struck him straight in the heart.
Al-Tabarani recorded it in al-Mu'jam al-Kabir; Qatadah too did not live in the time of Sayyiduna Sa'd (may Allah be pleased with him).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الطهارة / 1018