If, as I have often said, I worshipped wood and stone as God, I, too, should say to each, ‘Thou hast brought me forth.’ If I worship the images of the saints, or rather the saints, and worship and reverence the combats of the holy martyrs, how can you call these idols, senseless man? For idols are likenesses of false gods and adulterers, murderers and luxurious men, not of prophets or apostles. Listen whilst I take a telling and most true example of Christian and heathen images. The Chaldeans in Babylon had all sorts of musical instruments for the worship of idols who were devils, and the children of Israel had brought musical instruments from Jerusalem, which they hung upon the willow trees, and the instruments of both lutes and stringed instruments and flutes gave forth their music, these for the glory of God, the others for the service of devils. So must you look upon images and idols of heathens and Christians. Heathen idols were for the glory and remembrance of the devil; Christian images are for the glory of Christ, and of His apostles and martyrs and saints.
Translated by Mary H. Allies. Edition opa.patristics.john-of-damascus.on-holy-images.en.