Abu Juhayfah (may Allah be pleased with him) reported: I was with the Prophet (may Allah's peace and blessings be upon him) when he said to a man there: "I do not eat while reclining on my side."
Abu Juhayfah Wahb ibn ‘Abdullāh As-Sawā’i (may Allah be pleased with him) reports in this Hadīth that it was not of the practice of the Prophet (may Allah's peace and blessings be upon him) that he ate leaning on a pillow or something, putting his hand on the ground and reclining on it. The Prophet (may Allah's peace and blessings be upon him) would not sit this way because when doing so, one eats a lot. Eating a lot makes one lazy, and this results in physical problems. Leaning while eating entails that the food runs down the stomach in a way that is not straight, which is abnormal and could be harmful. Also, leaning while eating is position that indicates arrogance, which is not decorous.