What joy does the Nativity of the Mother of God bring us? Let us explain in more detail the Church hymn which explains the meaning of this feast’s joy. Through the birth of the Ever-Virgin, through Her only-begotten Son and God, cursed and outcast mankind makes peace with God Who is immeasurably offended by man’s sins, for Christ became the mediator of this peace (cf. Rom. 5:10-11). Man is freed from the curse and eternal death, made worthy of the blessing of the Heavenly Father; he is united and co-mingled with the Divine nature; he is raised to his first inheritance by this co-mingling, according to the Church hymn. Mankind, once an outcast, has been made worthy of sonship to the Heavenly Father, received the promise of the glorious resurrection and eternal life in the heavens together with the angels.
This has all been and is being wrought by the Son of God incarnate from the Most Pure Virgin from the Holy Spirit, and by the intercession of His Most Pure Mother. How honored and magnified is mankind through the Holy Virgin Mother of God, for it has been made worthy of renewal and sonship by God; She Herself was made worthy by Her immeasurable humility and exceedingly great purity and holiness to be the Mother of the God-man!St. John of Kronstadt, Sorrow and Joy: A Homily on the Day of the Nativity of the Most Holy Mother of God