Sahih al-Bukhari Book 74, Hadith 42

`Ali offered the Zuhr prayer and then sat down in the wide courtyard (of the Mosque) of Kufa in order to deal with the affairs of the people till the `Asr prayer became due. Then water was brought to him and he drank of it, washed his face, hands, head and feet. Then he stood up and drank the remaining water while he was standing. and said, "Some people dislike to drink water while standing thought the Prophet did as I have just done."