Nicea II (787), the Seventh Ecumenical Council:
We, therefore, following the royal pathway and the divinely inspired authority of our Holy Fathers and the traditions of the Catholic Church (for, as we all know, the Holy Spirit indwells her), define with all certitude and accuracy that just as the figure of the precious and life-giving Cross, so also the venerable and holy images, as well in painting and mosaic as of other fit materials, should be set forth in the holy churches of God, and on the sacred vessels and on the vestments and on hangings and in pictures both in houses and by the wayside, to wit, the figure of our Lord God and Saviour Jesus Christ, of our spotless Lady, the Mother of God, of the honourable Angels, of all Saints and of all pious people. For by so much more frequently as they are seen in artistic representation, by so much more readily are men lifted up to the memory of their prototypes, and to a longing after them; and to these should be given due salutation and honourable reverence (ἀσπασμὸν καὶ τιμητικὴν προσκύνησιν), not indeed that true worship of faith (λατρείαν) which pertains alone to the divine nature; but to these, as to the figure of the precious and life-giving Cross and to the Book of the Gospels and to the other holy objects, incense and lights may be offered according to ancient pious custom. For the honour which is paid to the image passes on to that which the image represents, and he who reveres the image reveres in it the subject represented. For thus the teaching of our holy Fathers, that is the tradition of the Catholic Church, which from one end of the earth to the other has received the Gospel, is strengthened. Thus we follow Paul, who spoke in Christ, and the whole divine Apostolic company and the holy Fathers, holding fast the traditions which we have received… Those, therefore who dare to think or teach otherwise, or as wicked heretics to spurn the traditions of the Church and to invent some novelty, or else to reject some of those things which the Church has received (
e.g. , the Book of the Gospels, or the image of the cross, or the pictorial icons, or the holy relics of a martyr, or evilly and sharply to devise anything subversive of the lawful traditions of the Catholic Church or to turn to common uses the sacred vessels or the venerable monasteries, if they be Bishops or Clerics, we command that they be deposed; if religious or laics, that they be cut off from communion.
https://www.newadvent.org/fathers/3819.htm