Today in church we chant the Service to the 630 Holy and God-bearing Fathers who
gathered together for the 4th Ecumenical Council in Chalcedon in 451.
The Council gathered to affirm Saint Cyril's teaching on the “hypostatic union” which was already considered by the Council of Ephesus in 431. In doing so, they condemned Eutyches who at the time was preaching that Christ is not made up of both divine and human natures, but divine only. This was among the many heresies that groups developed throughout the history of the early church.
For this reason, Saint Flavian who was the Patriarch of Constantinople, went on to have Eutyches excommunicated. However, the Patriach of Alexandria, Dioscorus, illegally received Eutyches back into communion and had Saint Flavian deposed.
We commemorate the fight to preserve the purity of the Orthodox Faith, as had first
been preached from Christ to the Apostles.
You are greatly glorified, O Christ our God, who established our Fathers as
luminaries upon the earth, and through them led us all to the true Faith. O Most
compassionate, glory to You.