Bede the Venerable
Catena Aurea · Markusevangelium 11
And they come to Jerusalem: and Jesus went into the temple, and began to cast out them that sold and bought in the temple, and overthrew the tables of the moneychangers, and the seats of them that sold doves; And would not suffer that any man should carry any vessel through the temple. And he taught, saying unto them, Is it not written, My house shall be called of all nations the house of prayer? but ye have made it a den of thieves. And the Scribes and Chief Priests heard it, and sought how they might destroy him: for they feared him, because all the people was astonished at his doctrine.
(ubi sup.) For they were in the temple for this purpose, either that they might persecute with corporal pains those who did not bring gifts, or spiritually kill those who did. The mind and conscience of the faithful is also the temple and the house of God, but if it puts forth perverse thoughts, to the hurt of any one, it may be said that thieves haunt it as a den; therefore the mind of the faithful becomes the den of a thief, when leaving the simplicity of holiness, it plans that which may hurt others.