The Sunday of Orthodoxy is the first Sunday of Great Lent. The dominant theme of this Sunday since 843 has been that of the victory of the icons. In that year the iconoclastic controversy, which had raged on and off since 726, was finally laid to rest, and icons and their veneration were restored on the first Sunday in Lent. Ever since, this Sunday has been commemorated as the "Triumph of Orthodoxy."
The Seventh Ecumenical Council dealt predominantly with the controversy regarding icons and their place in Orthodox worship. It was convened in Nicaea in 787 by Empress Irene at the request of Tarasios, Patriarch of Constantinople. The Council was attended by 367 bishops.
Almost a century before this, the iconoclastic controversy had once more shaken the foundations of both Church and State in the Byzantine empire. Excessive religious respect and the ascribed
miracles to icons by some members of society, approached the point of worship (due only to God) and idolatry. This instigated excesses at the other extreme by which icons were completely taken out of the liturgical life of the Church by the Iconoclasts. The Iconophiles, on the other-hand, believed that icons served to preserve the doctrinal teachings of the Church; they considered icons to be man's dynamic way of expressing the divine through art and beauty.
The Council decided on a doctrine by which icons should be venerated but not worshipped. In answering the Empress' invitation to the Council, Pope Hadrian replied with a letter in which he also held the position of extending veneration to icons but not worship, the last befitting only God.
The decree of the Council for restoring icons to churches added an important clause which still stands at the foundation of the rationale for using and venerating icons in the Orthodox Church to this very day: "We define that the holy icons, whether in colour, mosaic, or some other material, should be exhibited in the holy churches of God, on the sacred vessels and liturgical vestments, on the walls, furnishings, and in houses and along the roads, namely the icons of our Lord God and Saviour Jesus Christ, that of our Lady the Theotokos, those of the venerable angels and those of all saintly people. Whenever these representations are contemplated, they will cause those who look at them to commemorate and love their prototype. We define also that they should be kissed and that they are an object of veneration and honour (timitiki proskynisis), but not of real worship (latreia), which is reserved for Him Who is the subject of our faith and is proper for the divine nature. The veneration accorded to an icon is in effect transmitted to the prototype; he who venerates the icon, venerated in it the reality for which it stands".
An Endemousa (Regional) Synod was called in Constantinople in 843. Under Empress Theodora. The veneration of icons was solemnly proclaimed at the Hagia Sophia Cathedral. The Empress, her son Michael III, Patriarch Methodios, and monks and clergy came in procession and restored the icons in their rightful place. The day was called "Triumph of Orthodoxy." Since that time, this event is commemorated yearly with a special service on the first Sunday of Lent, the "Sunday of Orthodoxy".
Orthodox teaching about icons, as defined at the Seventh Ecumenical Council of 787, is embodied in the texts sung on this Sunday.