Musnad Abu Ya'la al-Mawsili 115:355

Ubayd Allah narrated to us, Khalid narrated to us, Sa'id narrated to us, from Qatadah, from Anas, that the Messenger of Allah (ﷺ) forbade drinking while standing. He said: And he was asked about eating while standing. Khalid said: I do not know who was asked. He said: "That is worse," or he said: "That is more foul."