John Chrysostom

But they are to be admired who brought in the paralytic, since on finding that they could not enter in at the door, they attempted a new and untried way. As it follows, And when they could not find by what way they might bring him in, they went upon the housetop, &c. But unroofing the house they let down the couch, and place the paralytic in the midst, as it follows, And they let him down through the things. Some one may say, that the place was let down, from which they lowered the couch of the palsied man through the things.

Catena Aurea by Aquinas ↗

Augustine of Hippo

The men then by whom he is let down may signify the doctors of the Church. But that he is let down with the couch, signifies that Christ ought to be known by man, while yet abiding in his flesh.

Catena Aurea by Aquinas ↗

Bede

And not finding by what way they might bring him in because of the crowd, they went up on the roof through the tiles. They desire to offer the paralytic to Christ but are excluded on all sides by the interposed crowd. Often, a soul, after the sloth of the lowly body, turns back to God and desires to be renewed by the remedy of heavenly grace but is delayed by the obstacle of old habit. …

On the Gospel of Luke ↗

Bonaventure

And because obstacles frequently arise for one who seeks through faith, therefore it is added: And not finding by what way they might bring him in because of the crowd, which is wont to impede approach to Christ; as it is said in Matthew 20 and below in chapter 18, that "the crowds rebuked the blind man, that he should be silent"; so also Zacchaeus, below in chapter 19, "sought to see Jesus, and could not because of the crowd." But certainly obstacles do not hold back true faith, but rather inflame it; in testimony of which it is …

Commentary on Luke, Chapter 5 ↗