Revelation 18:15

Those who became rich by her will stand afar off. Wherever the Spirit speaks of those made rich by her, it signifies the riches of sins. For lower down, where it is the voice of the unjust saying: Woe, woe, that great city, in which all who had ships at sea were made rich, the riches of things are understood. For they believe they have been made rich by the cleverness of their faction.

Whenever the Spirit says that they were made rich from her, he is indicating the abundance of their sins.… Can a city be dressed in fine linen and purple, rather than people? They lament for themselves, since they are despoiled of those riches mentioned here.… Can all those who are merchants and sailors and who work upon the sea be present to see the burning of a single city? Rather, it says that all who loved the world and were the workers of iniquity fear for themselves when they see the ruin of their own hope.

He leads before our eyes the sufferings of this Babylon, and through the laments made over her he depicts the greatness of her misfortune that she, who previously boasted of her royal majesty, will suffer.… He speaks figuratively of the present life as a "sea," since it is heaving with waves. Those who make commerce upon [the sea] swim in the turbulence of this life as though they were fishes. However, perhaps that city that suffers these things lies beside a physical sea and receives these misfortunes from those who sail upon it and receive from it an opportunity to loot it of its wealth. But it is necessary to add that the merchants of this universal Babylon, that is, Confusion, will suffer the same thing at the conclusion of the visible world and will sob inconsolably, since they are unwillingly deprived of the pleasures of this life and are reproached by their conscience because of their deeds.… But against this opinion is that of the ancient teachers of the church, which supposes that these things are prophesied against the Babylon of the Romans. They refer to the vision in which the ten horns are on the fourth beast, that is, upon the Roman rule, and from it another one comes that roots out three of the ten and subdues the others. And when this king of the Romans comes in the pretense of assisting and helping their rule, he in fact comes to effect their complete ruin. Therefore, as we said, whoever interprets this kingdom as though it were one body that from the beginning until now exercised power and which truly has shed the blood of apostles, prophets and martyrs, such a one would not be mistaken concerning the present passage. For even as it is said that there is one chorus and one army and one city, although those who populate each of these might change, so also there is one kingdom, although it is divided into many times and places.