During the season of Lent, each of the five Sundays carries a certain theme. The theme of the first Sunday, called the Sunday of Orthodoxy, is the Restoration of Icons, based on the historical proclamation of the same which took place on the first Sunday in Lent (March 11) in the year 843.
This proclamation was so essential to Orthodox faith and practice that it became a permanent element of the Church's liturgical cycle, itself the truest expression of the Orthodox Christian Faith.
Lex orandi lex credendi – the rule of praying is the rule of believing. The Sunday of Orthodoxy epitomizes this ancient maxim of the Church.
The presence of icons and their use defines the Christian Faith. As the Church declared in its definition of faith at the Seventh Ecumenical Council (787 A.D.) dealing with the heresy of iconoclasm (lit., the "smashing/destruction of icons), not only is the Church allowed to have icons, but the Church must have icons. Now this truth stands boldly at the end of the first week of Lent ushering in the rest of the season of repentance presenting what is normal in the Christian way of life.
So, why are icons essential? What are icons, and how do they define Christianity?
Quite simply an icon (Gk., eikon) is an image made with some kind of physical medium, such as wood, paint, fabric, or stone. Icons also include images, or objects, of human origin, for instance, the bodies, bones, and possessions of saints; these are typically known as relics. Icons are images of the Savior Jesus Christ and all those persons and things sanctified in Him: His mother the Virgin Mary, other holy people, the Cross, and the Church itself (church buildings are icons in architecture), made specifically to depict their divine character in created form.
The icon of Christ is the defining image. "He is the image (Gk., eikon) of the invisible God, the firstborn over all creation" (Col. 1:15; cf. 2 Cor. 4:4 & Heb. 1:3). Furthermore, "For in [Christ] dwells all the fullness of the Godhead bodily; and you are complete in Him, who is the head of all principality and power" (Col. 2:9-10; cf. Jn. 1:14).
Icons convey the dual nature of our existence according to God’s original design which is restored in the Person of Jesus Christ the God-Man: creatures partaking of God's divine, eternal life in communion with God and one another. "Then God said, 'Let Us make man in Our image (Gk., eikon), according to Our likeness' …So God made man; in the image of God He made him; male and female He made them” (Gen. 1:26, 27). Jesus Christ is the Icon, and we know what He looks like because He became man (so, we make images of Him); likewise, in Christ, all human beings are to be icons, and we make images of persons and objects imbued with the holiness and grace of God.
Icons are essential because they epitomize God's plan of salvation outlined from the beginning of the world. The Church can no more do without icons than it can do without Christ Himself – its Head – and the Christians who comprise it – the Body of Christ. Even the Old Covenant focused on reconciliation and communion with God in the worship of the Tabernacle and then Temple, and these were filled with icons (images) hammered from gold, carved in wood, and embroidered in fabric: the Ark of the Covenant, the Lampstand, the Table of Showbread, the Altar, cherubim (angels), oxen, and palm trees, plus the Priests and Levites in their prescribed vestments (see Ex. 25-30; 3 Kgm. 6-8). All pointed forward to their fulfillment in the Person of Christ, His mother the Virgin Mary, and the saints in the Church.
In the 8th and 9th centuries, the struggle to defend and restore the icons reached the point of martyrdom for some of the faithful. Their witness unto death is the reason we retain this theme at the start of Lent each year. We too are called to be genuine images of the divine life we have from God in Christ, our crucified and risen Savior.