The Damascene and the Icons

in Christian liturgy:

...The controversy surrounding Iconoclasm had arisen. Some Christians, worried that the relics of saints and images of Christ had taken an inappropriate place within the public spiritual life of Christianity, agitated to have those relics and images suppressed by the Byzantine emperor. Also persuasive was the fact that vast swaths of imperial territory had been lost to armies conquering in the name of a religion which forbade the depiction of the human form as idolatry. Perhaps the Almighty had chastised a Christian civilization for generating images of Christ.
John of Damascus opposed the movement to abolish images, and he rooted his opposition in an understanding of salvation history and Christ’s unique revelatory role:

Previously God, who has neither a body nor a face, absolutely could not be represented by an image. But now that he has made himself visible in the flesh and has lived with men, I can make an image of what I have seen of God . . . and contemplate the glory of the Lord, his face unveiled. (CCC 1159 n.27)

The “Dispensation” or “Economy” of salvation had included the Incarnation of God in Jesus Christ. Therefore, argued John, the Church in its own task of dispensing grace in God’s household properly uses images of Christ to help mankind contemplate the divine.
John’s theological opposition to the destruction of images was later promulgated as Church doctrine by the Council of Nicaea:

Following the divinely inspired teaching of our holy Fathers and the tradition of the Catholic Church (for we know that this tradition comes from the Holy Spirit who dwells in her) we rightly define with full certainty and correctness that, like the figure of the precious and life-giving cross, venerable and holy images of our Lord and God and Savior, Jesus Christ, our inviolate Lady, the holy Mother of God, and the venerated angels, all the saints and the just, whether painted or made of mosaic or another suitable material, are to be exhibited in the holy churches of God, on sacred vessels and vestments, walls and panels, in houses and on streets. (CCC 1161 n.31)...