Sunday of the Holy Fathers of the 4th Ecumenical Council
On the Sunday that falls from the 13th to the 19th of the present month, we chant the Service to the 630 Holy and God-bearing Fathers who came together for the 4th Ecumenical Council who assembled in Chalcedon in 451, to condemn Eutyches, who taught that there was only one nature, the divine, in Christ after the Incarnation, and Dioscorus, Patriarch of Alexandria, who illegally received Eutyches back into communion and deposed Saint Flavian, Patriarch of Constantinople, who had excommunicated Eutyches.
In the Slavic tradition, on this Sunday, the Fathers of the first six Ecumenical Councils are all commemorated.