Musnad Ahmad 5:575

Muhammad ibn Ja‘far narrated to us, Shu‘bah narrated to us, from al-Hakam, from ‘Ali ibn al-Husayn, from Marwan ibn al-Hakam, that he said: I witnessed ‘Ali and ‘Uthman between Makkah and Madinah, and ‘Uthman was forbidding the *mut‘ah* (combining Hajj and ‘Umrah) and that they be combined. When ‘Ali saw that, he entered into the state of *ihram* for both of them, saying: "Here I am, for ‘Umrah and Hajj together." ‘Uthman said: "Do you see me forbidding the people from it, while you do it?" He said: "I would not abandon the Sunnah of the Messenger of Allah (may Allah bless him and grant him peace) for the saying of anyone among the people." *** ‘Abdullah narrated to us, my father narrated to me, and Ishaq ibn Isma‘il, they both said: Ibn Fudayl narrated to us, from ‘Ata’ ibn al-Sa’ib; and Sufyan ibn Waki‘ narrated to me, ‘Imran ibn ‘Uyaynah narrated to us, all of them from ‘Ata’ ibn al-Sa’ib, from Maysarah: I saw ‘Ali drink while standing. I said: "Do you drink while you are standing?" He said: "If I drink while standing, I have seen the Messenger of Allah (may Allah bless him and grant him peace) drink while standing; and if I drink while sitting, I have seen the Messenger of Allah (may Allah bless him and grant him peace) drink while sitting."