Ali bin Abu Talib drank while standing, and the people looked at him as if they disapproved. He said, "Why are you looking at me? If I drink standing, I have seen the Prophet ﷺ drink standing, and if I drink sitting, I have seen the Prophet ﷺ drink sitting."
أن علي بن أبي طالب شرب قائما، فنظر إليه الناس كأنهم أنكروه، فقال: ما تنظرون؟ إن أشرب قائما فقد رأيت النبي ﷺ يشرب قائما، وإن أشرب قاعدا فقد رأيت النبي ﷺ يشرب قاعدا.
Ahmad narrated it (795) from Affan, who said, Hammad narrated to us, from Ata bin Saaib, from Zazan, and he mentioned it.Its chain of transmission is sahih. Ata bin Saaib is trustworthy, and the leading scholars affirmed his trustworthiness, except that his memory became confused later in life. However, Hammad bin Salama was among those who narrated from him before that confusion occurred.