Rashi citing Targum Yonasan: It is in order to stoke coals of fire, like we find "va'Yishlach ha'Keruv Es Yado?" (10:7). Human hands take coals from the fire and give them to the Keruv, and the Keruv to the Shali'ach, in order that the coals will cool down from hand to hand, to lighten Yisrael's punishment.

Malbim: Even though their legs are unlike people's, it teaches that they look like people with two arms and two legs, and not like animals with four legs and no arms. The arms are under their wings; they are exposed only when they lift their wings; when their wings lie on the body, the arms are covered.

Malbim (according to the metaphor): When they go with their legs and do not fly - they conduct according to nature and Ma'arachah, the hands are covered, and the human hands are not seen, only the Raglei Chayah are seen. Their actions are forced, like those of animals that have no choice to change their actions. When they lift their wings to fly, i.e. they change the Ma'arachah, they conduct according to Hashem's desire and His command based on choice. Then their actions are like acts of a man, who chooses and he is not forced in his actions. This will be when Yisrael repent. The Ma'arachah will change and the human hands will be seen. Chazal said, human hands are under their wings to accept Ba'alei Teshuvah.

Malbim according to the Rambam: The arms were attached to the body under where the wings were attached.

Pesachim 119a: The Kesiv refers to Hashem's hand. It is under their wings in order to receive Teshuvah of penitents out of 'sight' of Midas ha'Din (which would protest).

Radak: The Kesiv teaches that its hand is like a human hand, as if it wrote v'Yadav Yedei Adam. This is like "Einayich Yonim" (Shir ha'Shirim 1:15) - they are like doves' eyes.

Rashi: In the four directions of the world, for they have faces and wings in every direction ¹ .

Malbim: Just like the wings used to fly are fixed on all four sides, by every face, to be able to fly in any direction, so the hands are fixed on all four sides.

Malbim (according to the metaphor): On every side that they raise wings to rise above the Ma'arachah, whether for Chesed, Din or mercy, their actions are with choice and desire. They are not forced via the Ma'arachah, rather, according to Hashem's desire.

Malbim according to the Rambam: The two arms were for all four faces of each Chayah, just like each has only two legs. From where the arms join to the body and below, they are one body; only above the arms they separate to four faces.

Rashi citing Targum Yonasan: They are the same for all four of them.

Malbim: Their wings are with their faces; there are wings for every face. We need u'Fneihem? lest we err to say that l'Arbatam means for each Chayah. This is like the opinion that there were as many hands as wings - two hands for every [pair of] wing[s].

Malbim according to the Rambam: Above the arms were four faces, and [two] wings for every face.