The divine injunction included the prohibition of every representation of God by the hand of man. Deuteronomy explains: “Since you saw no form on the day that the Lord spoke to you at Horeb out of the midst of the fire, beware lest you act corruptly by making a graven image for yourselves, in the form of any figure….” It is the absolutely transcendent God who revealed himself to Israel. “He is the all,” but at the same time “he is greater than all his works.” He is “the author of beauty.”
Nevertheless, already in the Old Testament, God ordained or permitted the making of images that pointed symbolically toward salvation by the incarnate Word: so it was with the bronze serpent, the ark of the covenant, and the cherubim.
Basing itself on the mystery of the incarnate Word, the seventh ecumenical council at Nicaea (787) justified against the iconoclasts the veneration of icons – of Christ, but also of the Mother of God, the angels, and all the saints. By becoming incarnate, the Son of God introduced a new “economy” of images.
The Christian veneration of images is not contrary to the first commandment which proscribes idols. Indeed, “the honor rendered to an image passes to its prototype,” and “whoever venerates an image venerates the person portrayed in it.”The honor paid to sacred images is a “respectful veneration,” not the adoration due to God alone:
Religious worship is not directed to images in themselves, considered as mere things, but under their distinctive aspect as images leading us on to God incarnate. the movement toward the image does not terminate in it as image, but tends toward that whose image it is.
From the Catechism of the Catholic Church 2129-2132