Riyad as-Salihin 768
Ibn 'Umar (May Allah be pleased with them) reported:
During the lifetime of the Messenger of Allah (ﷺ) we would eat while walking and would drink while standing. [At- Tirmidhi] .
وعن ابن عمر رضى الله عنهما قال‏:‏كنا نأكل على عهد رسول الله صلى الله عليه وسلم ونحن نمشى ، ونشرب ونحن قيام‏.‏((رواه الترمذي))