For this reason God said (immediately after he gave the commandment, Thou shalt have no other gods before me): Thou shalt make no carved or graven image. Thou shalt make no likeness of anything in the heavens above or the earth below or that is in the water. Thou shalt not worship them. Thou shalt not venerate them. I am your God, a strong and vengeful God, a jealous God who punishes the sons for the sins of their fathers (Exodus 20[:4ff.]).
See how God prohibits any kind of image because men are frivolous and are inclined to worship them. For this reason God said: Thou shalt not worship them, thou shalt not honour them. Thereby God prohibits all veneration and smashes the refuge of the papists who at all times do violence to Scripture through their subtlety and make black out of white, evil out of good. Thus if one were to say: Indeed, I do not worship images; I do not venerate them for themselves, but for the sake of saints which they signify. God’s answer is short and clear.
Thou shalt not worship them. Thou shalt not venerate them. Make whatever gloss you can, thou shalt absolutely not worship them, thou shalt not bend thy knee before them, thou shalt not light a candle before them. God says: If I had wanted you to venerate me or my saints in pictures, I would not have forbidden you to make pictures and likenesses.
Now I want to prove that Christians must confess that they venerate their idols. The grounds [for the proof]: because they bow and scrape before them (for the sake of dead holy men) I can definitely conclude that they venerate images. For if I venerate a marshal in the name of the prince he serves, I venerate both him and his prince. I venerate the servant as the servant of the prince, and do so before I venerate the prince. Thus it cannot be denied that some of the veneration goes to him as a servant. Therefore, when I venerate an image because of God, I truly venerate that which God has forbidden.*
Now I will ask in addition, is it a trifling honour that we call images saints? If we were willing to think clearly, we would find that we deflect honour from the true saints and transfer it to deceitful pictures of them. Therefore, we are calling images saints and attributing sanctity to them.
Moreover, it cannot be denied that it is a great honour to be on the altar. Indeed, the pope deems it such an honour that he permits no pious layman to stand or recline on an altar. It is truly a great and high honour when you put someone in the place where one handles the body of Christ, where God alone should be invoked, on the altar that has been established for the special honour of God, for his own veneration.
* The defence of the cult of images rested traditionally on the idea of vicarious veneration (the image taking the place of the saint as the marshal takes the place of the absent prince). According to this theory any cult directed to the image (as respect shown to the marshal) goes to the saint represented therein, so that the physical object (like the marshal) is not venerated per se. This was the doctrine of the prototype as outlined by St Basil.