Ibn 'Umar (May Allah be pleased with them) reported:
During the lifetime of Messenger of Allah (ﷺ) we would eat while walking and would drink while standing.[At- Tirmidhi]. (RU)
App reference (RU): Book 3, Hadith 42 (RU)
Arabic/English book reference (RU): Book 3, Hadith 769 (RU)