Bukhari

Hadith Commentary:

Both of these ahadith establish the prohibition of eating while reclining. However, Ibn Abi Shaybah has also transmitted its permissibility from Ibn Abbas and Khalid bin Walid (radi Allahu anhum) and others. But the action of the Prophet (sallallahu alayhi wa sallam) himself is present, before which all others are insignificant.

Hadith Commentary:
(1)
Some individuals are of the opinion that eating while reclining was something specific to the Messenger of Allah (sallallahu alayhi wa sallam), and that it is not prohibited for the ummah. Imam Bayhaqi rahimahullah has refuted this, stating that it is also disliked (makruh) for others to do so, because it is the practice of the arrogant. However, due to an excuse, it is permissible to eat while reclining. Yet, Ibn Abbas, Khalid bin Walid (radi Allahu anhum), Ubaidah Salmani, Muhammad bin Sirin, Ata bin Yasar, and Imam Zuhri (rahimahumullah) are of the view that eating while reclining is permissible in an absolute sense.
(Fath al-Bari: 9/670)
According to our inclination, eating while reclining is permissible, but with dislike (karahah).
It is permissible because the Messenger of Allah (sallallahu alayhi wa sallam) did not prohibit it, and it is disliked because it is contrary to the practice of the Messenger of Allah (sallallahu alayhi wa sallam).

(2)
It is recommended (mustahabb) for the one eating to adopt one of the following postures while eating:
• Sit on one's knees as is done in the tashahhud position.
• Raise the right knee and lay the left foot flat on the ground.
(Fath al-Bari: 9/671)

(3)
The dislike (karahah) of eating while reclining is because of the fear that it may lead to the enlargement of the belly, as Ibrahim al-Nakha'i rahimahullah has transmitted from the predecessors (salaf).
(al-Musannaf of Ibn Abi Shaybah: 5/140)

Explanation:
1:
What does it mean to recline while eating? Several points are mentioned in this regard:

(1)
Leaning to one side while eating, such as resting on the right or left hand or elbow,

(2)
Sitting cross-legged on a mattress spread on the ground for comfort and ease so that one may eat more,
Some people say that calling this manner of sitting "reclining" is not correct.
Hafiz Ibn Hajar rahimahullah states that the recommended way of sitting is to sit on the knees with the soles of the feet on the ground,
or to keep the right foot upright and sit on the left.

Benefit:
From this hadith, it is understood that one should not eat while reclining on a cushion, because there is arrogance in it; rather, one should eat with humility.