Maisarah (may Allah have mercy on him) says: I saw that on one occasion, Sayyiduna Ali (may Allah be pleased with him) drank water while standing. I said to him, "You are drinking water while standing?" He replied: "If I have drunk water while standing, it is because I saw the Prophet (peace and blessings be upon him) do so, and if I have drunk while sitting, I have seen him do that as well."
Hadith Referenceمسند احمد / مسند الخلفاء الراشدين / 916
Hadith Gradingحکم دارالسلام:حسن لغيره، ابن فضيل - وإن كان روي عن عطاء بعد الاختلاط - قد توبع