Augustine of Hippo

Let no one therefore do ought in the oratory, but that for which it was made and whence it got its name. It follows, But ye have made if a den of thieves. (de Cons. Ev. ii. 68.) It is manifest that the Lord did this thing not once but twice; the first time is told by John, this second occasion by the other three.

Catena Aurea by Aquinas ↗

Gregory the Dialogist

About this temple it is soon added: "My house is a house of prayer, but you have made it a den of thieves." For those who sat in the temple to receive gifts, it was certainly not doubtful that they would seek to harm those who gave nothing. Therefore the house of prayer had been made a den of thieves, because they knew how to stand in the temple for this purpose: either to eagerly pursue bodily those not giving gifts, or to kill spiritually those who did give. …

Forty Gospel Homilies, Homily 39 ↗

Thomas Aquinas

"And he said to them: it is written" etc.; here he reproves them. And first in that which pertains to the dignity of the temple; secondly, in that which pertains to its use. "It is written," namely (Isa 56:7), "my house is a house of prayer." The explanation of this is found in 3 Kings 8:27, where it says, "If heaven and the heavens of heavens cannot contain thee, how much less this house which I have built for thee?" Hence it is not called the house of the Lord because he corporally inhabits it, but because it is a place appointed …

Commentary on Matthew ↗