The Horos of the Second Council of Nicea (AD 787)
To summarize, we declare that we defend free from any innovations all the — written and — unwritten ecclesiastical traditions that have been entrusted to us.
One of these is the production of representational art; this is quite in harmony with the history of the spread of the gospel, as it provides confirmation that the becoming man of the Word of God was real and not just imaginary, and as it brings us a similar benefit. For, things that mutually illustrate one another undoubtedly possess one another's message.
Given this state of affairs and stepping out as though on the royal highway, following as we are the God-spoken teaching of our holy fathers and the tradition of the catholic church — for we recognize that this tradition comes from the Holy Spirit who dwells in her — we decree with full precision and care that, like the figure of the honored and life-giving cross, the revered and holy images, whether painted or made of mosaic or of other suitable material, are to be exposed in the Holy Churches of God, on sacred instruments and vestments, on walls and panels, in houses and by public ways, these are the images of our Lord, God and savior, Jesus Christ, and of our Lady without blemish, the holy God-bearer (theotokos), and of the revered angels and of any of the saintly holy men.
The more frequently they are seen in representational art, the more are those who see them drawn to remember and long for those who serve as models, and to pay these images the tribute of salutation and respectful veneration. Certainly this is not the full adoration (latria) in accordance with our faith, which is properly paid only to the divine nature, but it resembles that given to the figure of the honored and life-giving cross, and also to the holy books of the gospels and to other sacred cult objects. Further, people are drawn to honor these images with the offering of incense and lights, as was piously established by ancient custom. Indeed, the honor (proskynesis) paid to an image traverses it, reaching the model, and he who venerates the image, venerates the person represented in that image.
So it is that the teaching of our holy fathers is strengthened, namely, the tradition of the Catholic Church which has received the gospel from one end of the earth to the other.