Maisarah (may Allah have mercy on him) and Zadhan say that once Sayyiduna Ali (may Allah be pleased with him) drank water while standing, and said: If I have drunk water standing, it is because I saw the Prophet (peace and blessings of Allah be upon him) do so, and if I have drunk sitting, I have seen him do that as well.
Hadith Referenceمسند احمد / مسند الخلفاء الراشدين / 1125
Hadith Gradingحکم دارالسلام:حسن لغيره، خالد بن عبدالله الواسطي روي عن عطاء بعد الاختلاط ، لكن توبع