This couplet was inspired by icons of the Theotokos of the Unburnt Bush and medieval titles of the Immaculate Virgin Mary as a pure fountain or wellspring.
Meanwhile Moses was tending the flock of his father-in-law Jethro, the priest of Midian. Leading the flock beyond the wilderness, he came to the mountain of God, Horeb. There the angel of the Lord appeared to him as fire flaming out of a bush. When he looked, although the bush was on fire, it was not being consumed. So Moses decided, “I must turn aside to look at this remarkable sight. Why does the bush not burn up?” When the Lord saw that he had turned aside to look, God called out to him from the bush: Moses! Moses! He answered, “Here I am.” God said: Do not come near! Remove your sandals from your feet, for the place where you stand is holy ground. I am the God of your father, he continued, the God of Abraham, the God of Isaac, and the God of Jacob. Moses hid his face, for he was afraid to look at God.Exodus 3:1-6
Christian tradition has seen in the marvelous theophany of the unburnt bush a type of the Most Holy Theotokos, which means “God bearer.” As the bush on Mount Horeb was not consumed by the fiery presence of God, Mary’s virginal integrity was preserved in conceiving by the power of the Holy Spirit and in giving birth to the Son of God. Icons of the Theotokos of the Unburnt Bush venerate the mystery of the Virgin birth of Christ and the sinless purity of the All-Holy Mother of God, the Panagia.
The third antiphon for Evening Prayer on the Solemnity of Mary, Mother of God (January 1) in the Liturgy of the Hours reads: “Your blessed and fruitful virginity is like the bush, flaming yet unburned, which Moses saw on Sinai. Pray for us, Mother of God.”
The dogma of the Immaculate Conception defined by Pope Pius IX on 8 December 1854 proclaimed that the Blessed Virgin Mary “in the first instance of her conception, by a singular privilege and grace granted by God, in view of the merits of Jesus Christ, the Saviour of the human race, was preserved exempt from all stain of original sin.”
In the centuries leading up to the dogma, a litany of titles extolling Mary for her singular purity under the symbol of a fountain or wellspring abounded in medieval piety:
Sealed fountainFountains as Marian Symbols by Sister M. Danielle Peters
Sealed and closed fountain
Sealed fountain of purity
Clear as a fountain
Fountain of extraordinary sweet and loving virtues
Fountain of sanctity and goodness
Fountain of dew
Free fountain of paradise
Fountain continuously refreshing the dry lands
Fountain of all piety free of all pollution and corruption
Fountain of utter clarity because there is no pollution in your water
A bottomless well
The Scriptural basis for the fountain as a symbol of the Virgin Bride comes from the Song of Songs:
A garden enclosed, my sister, my bride,Song of Songs 4:15
a garden enclosed, a fountain sealed!
Bush flaming yet unburned on God’s holy mountain:
Hail, Virgin, full of grace, sealed and pure fountain!