Sayyiduna Abu Juhaifah (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) said: "I do not eat while reclining (or resting on a cushion)."
Hadith Referenceسنن دارمي / من كتاب الاطعمة / 2108
That is, the manner in which I eat is that I do not eat while reclining or resting against a cushion.
To eat while reclining or resting against a cushion is a sign of arrogance and pride; for this reason, the Prophet (sallallahu alayhi wa sallam) refrained from eating in this manner. Some scholars have said that this is a sign of the non-Arabs (Ahl al-‘Ajam).
The Prophet (sallallahu alayhi wa sallam) would eat while sitting on his knees (two knees) or by spreading one leg and keeping the other upright, which is a sign of humility and modesty. Sitting cross-legged (with both legs folded under) and eating has been considered by scholars as a sign of worldly people, which leads to the habit of overeating, and a person eats excessively, causing the belly to protrude. In the aforementioned hadith, there is an indication that a person should not sit in such a spread-out manner that it leads to eating more.