Cyril of Alexandria

There are again some who bear faith about them, as if it consisted in the nakedness of words; their faith is without root, of whom it is added, And some fell upon a rock, and as soon as it sprung up, it withered away, because it lacked moisture.

Catena Aurea by Aquinas ↗

Bede

"And some fell on rocky ground, and when it came up, it withered because it had no moisture." Here he correctly identifies the rocky ground as a hard and unyielding heart, unpenetrated by the plow of true faith. Moisture at the root of the seed is akin to the oil for the lamps of the virgins in another parable, meaning love and the perseverance of virtue.

On the Gospel of Luke ↗

Bonaventure

The second difference of soil, however, is that which receives and in a certain way retains, but does not nourish: and with regard to this he adds: And some fell upon the rock, that is, upon a hard heart, of which Zechariah seven says: "They made their heart as adamant"; and Job forty-one: "His heart shall be hardened as a stone." This soil, although it can retain the seed, nevertheless cannot nourish it, since moisture is lacking; and therefore he adds: And having sprung up, it withered away, because it had no moisture, namely, …

Commentary on Luke, Chapter 8 ↗