"The Messenger of Allah forbade us to urinate while standing." (Da'if)
I heard Muhammed bin Yazid, Abu 'Abdullah, say: "I heard Ahmad bin 'Abdur-Rahman Al-Makhzumi say: 'Sufyan Ath-Thawri said concerning the Hadith of 'Aisha- 'I (always) saw him urinating whilst sitting down' - a man knows more about that (about such matters) than she.' Ahmad bin 'Abdur-Rahman said: 'It was the custom of the Arabs to urinate standing up. Do you not see that in the Hadith of 'Abdur-Rahman bin Hasanah it was said: 'He sits down to urinate as a woman does.'"
I heard Muhammed bin Yazid, Abu 'Abdullah, say: "I heard Ahmad bin 'Abdur-Rahman Al-Makhzumi say: 'Sufyan Ath-Thawri said concerning the Hadith of 'Aisha- 'I (always) saw him urinating whilst sitting down' - a man knows more about that (about such matters) than she.' Ahmad bin 'Abdur-Rahman said: 'It was the custom of the Arabs to urinate standing up. Do you not see that in the Hadith of 'Abdur-Rahman bin Hasanah it was said: 'He sits down to urinate as a woman does.'"
Sunan Ibn Majah Book 1, Hadith 43