Divine Liturgy of the Holy Forefathers.

The Sunday that falls between December 11-17 is known as the Sunday of the Holy Forefathers. These are the ancestors of Christ according to the flesh, who lived before the Law and under the Law, especially the Patriarch Abraham, to whom God said, “In thy seed shall all of the nations of the earth be blessed” (Gen. 12:3, 22:18).

This was taken from: https://www.oca.org/saints/lives/2021/12/12