Commemorated on the Sunday that falls between the 11th and 17th of December

On this Sunday, in preparation of the Nativity of our Lord, we remember the Patriarch Abraham and his lineage, ancestors of Christ. The story of Abraham and his faithfulness should be read in the Book of Genesis.
  "Through the connection of the holy Ancestors and Patriarchs, Our Saviour Jesus Christ is Himself also, in a way, the fruit of the faith of Abraham. So, when God makes his voice known to each of us while we are still in the strange land of the passions and worldly vanities, we must like Abraham unhesitatingly leave all that is ours, and follow the divine calling with faith until we reach the Promised Land where, in our turn, we shall be able to give birth spiritually to Christ For, planted in us by faith and Baptism, He has to grow in us through the virtues so as to shine in the light of contemplation. We descendants of Abraham, 'children of the promise' as Isaac was, having become 'sons of God' through the gift of the Holy Spirit, out therefore to see Christ form in us... Let us then for our part become forebears of Christ and continue steadfast in the faith, so that we may keep the feast of his Nativity, saying: It is no longer I who live, but Christ who lives in me." (Synaxarion)