Anna was to be the mother of the Virgin Mother of God, and hence nature did not dare to anticipate the flowering of grace. Thus nature remained sterile, until grace produced its fruit. For she who was to be born had to be a first born daughter, since she would be the mother of the first-born of all creation, in whom all things are held together.
Joachim and Anna, how blessed a couple! All creation is indebted to you. For at your hands the Creator was offered a gift excelling all other gifts: a chaste mother, who alone was worthy of him.
And so rejoice, Anna, that you were sterile and have not borne children; break forth into shouts, you who have not given birth. Rejoice, Joachim, because from your daughter a child is born for us, a son is given us, whose name is Messenger of great counsel and universal salvation, mighty God. For this child is God.
Joachim and Anna, how blessed and spotless a couple! You will be known by the fruit you have born, as the Lord says: By their fruits you will know them. The conduct of your life pleased God and was worthy of your daughter. For by the chaste and holy life you led together, you have fashioned a jewel of virginity: she who remained a virgin before, during and after giving birth. She alone for all time would maintain her virginity in mind and soul as well as in body.
Joachim and Anna, how chaste a couple! While safeguarding the chastity prescribed by the law of nature, you achieved with God’s help something which transcends nature in giving the world the Virgin Mother of God as your daughter. While leading a devout and holy life in your human nature, you gave birth to a daughter nobler than the angels, whose queen she now is. Girl of utter beauty and delight, daughter of Adam and mother of God, blessed the loins and blessed the womb from which you come! Blessed the arms that carried you, and blessed your parents’ lips, which you were allowed to cover with chaste kisses, ever maintaining your virginity. Rejoice in God, all the earth. Sing, exult and sing hymns. Raise your voice, raise it and do not be afraid.
Source: Homily on the Nativity of the Theotokos (PG 96:663)