It was narrated that 'Aishah said: If anyone tells you that the Messenger of Allah urinated while standing, do not believe him, for I (always) saw him urinating while sitting down.
It was narrated that 'Umar said: The Messenger of Allah saw me urinating while standing, and he said: 'O 'Umar, do not urinate standing up.' So I never urinated whilst standing after that.
It was narrated that Jabir bin 'Abdullah said: 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.'