Musnad Ahmad 32:398

Muhammad ibn Ja'far and Muhammad ibn Bakr narrated to us, they said: Sa'id narrated to us, from Qatadah, from Anas ibn Malik, who said: "The Messenger of Allah, may Allah bless him and grant him peace, forbade that a man should drink while standing." He said: So we said to Anas: "What about eating?" He said: "That is worse, or more foul." Ibn Bakr said: "Or more vile."