John Chrysostom

Now all the rest He doth as on the former occasion; thus He both makes them sit down on the ground, and He makes the loaves multiply themselves in the hands of the disciples. For, "He commanded," it is said, "the multitude to sit down on the ground. And He took the seven loaves, and the fishes, and gave thanks, and brake, and gave to His disciples, and the disciples to the multitude."

Homily on the Gospel of Matthew 53 ↗

Hilary of Poitiers

The multitudes sit down on the ground; for before they had not reposed on the works of the Law, but they had supported themselves on their own sins, as men standing on their feet.

Catena Aurea by Aquinas ↗

Thomas Aquinas

And he commanded the multitude to sit down upon the ground. Here the arrangement is set forth. And first, he arranges them; second, he takes the material; third, he gives thanks, and breaks, and distributes. He says therefore and he commanded. In the other feeding it says that he made them recline upon the grass. By grass, temporal things are signified; hence Isa. 40:6: all flesh is grass, and all the glory thereof as the flower of the field. …

Commentary on Matthew ↗