Sunan Ibn Majah
Hadith #309
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