Although icons had been used in churches, in the early 8th century AD, the eastern Roman Emperor began a campaign against icons. The emperor ordered his soldiers to remove icons from churches, monasteries, public places and so on. No one is entirely sure why the emperor ordered this. Some think it was because of the Old Testament commandment forbidding the worship of graven images. In any case, many Christians suffered because of their defense of icons.
In 787 AD the Empress Irene, who was ruling in place of her young son, called a council of bishops to defend icons. Many bishops gathered and the veneration of icons was declared to be not only permissible, but even necessary. This council, known as the second council of Nicea, is considered the seventh ecumenical council. However, later emperors renewed the campaign against icons. It was not until 843 AD, when the empress Theodora ordered the restoration of icons that the iconoclasm, or the campaign against icons, ended. This was on the first Sunday of Lent that year and since then the first Sunday of Lent commemorates this event. This is known as the Sunday of Orthodoxy.
The Fathers of the church taught that we venerate icons, not worship them. Worship is due only to God, when we venerate an icon, we are not venerating wood and paint, but rather the person or persons depicted on the icon. We can do this because Jesus Christ became a genuine human being.
The essence of Christianity is that God, in the person of Jesus Christ, became a human being order to save humanity. As human beings we are not imprisoned in bodies, as some Greek philosophers taught, but we are unities of body, mind and spirit.
Therefore, the whole human person participates in the process of salvation and this includes the veneration of icons. And so icons are not simply religious pictures which can be used or not used according to taste, but rather they make the essential dogmatic point that Jesus Christ is true God and true man, and came to save the whole person. This is what the church proclaims on the Sunday of Orthodoxy.
Troparion — Tone 2
We venerate Thy most pure image, O Good One, / and ask forgiveness of our transgressions, O Christ God. / Of Thine own will Thou wast pleased to ascend the Cross in the flesh / to deliver Thy creatures from bondage to the enemy. / Therefore with thanksgiving we cry aloud to Thee: / Thou hast filled all with joy, O our Savior, / by coming to save the world.
Kontakion — Tone 8
No one could describe the Word of the Father; / but when He took flesh from you, O
Theotokos, He accepted to be described, / and restored the fallen image to its former
beauty. / We confess and proclaim our salvation in word and images.