One of the less-well-known Advent hymns is “Rorate Caeli Desuper” (Heavens, drop dew from above). It is a plaintive hymn that recalls our desperate need for a savior and concludes with consolations from God, who has heard our cries and hastens to save us.
The refrain, which comes from Isaiah 45:8, is shown below in both Latin and English:
Roráte caéli désuper, (Heavens, drop dew from above)
et núbes plúant jústum. (and let the clouds rain forth justice).
This is an image for the gentle work of the Holy Spirit. The Spirit works subtly like the dewfall and more boldly like rainfall to bring forth Him who is our justice. For indeed, dew and rain are symbols of life, vigor, and/or providence. Water is also a symbol of the Holy Spirit. The Archangel St. Gabriel told Mary, The Holy Spirit shall come upon you, and the power of the most High shall overshadow you. And therefore also the Holy which shall be born of thee shall be called the Son of God (Luke 1:35). Like a gentle dewfall, the Holy Spirit overshadows Mary and quietly she conceives; He who is our justice begins to dwell among us.
The rains that come forth from the clouds also are an image of God’s work in the Incarnation. Isaiah 45:8 continues by saying, Let the earth open up that salvation may sprout and righteousness spring up with it; I, the LORD, have created it. As God’s grace comes forth like rain from the clouds, truth shall spring up from the earth (see Psalm 85:11). Indeed, we are of the dust of this earth, and as the Lord tabernacles Himself in flesh in the womb of the Blessed Mother, justice and truth spring up from the earth as well. Both the quiet dewfall and the rain bring forth Him who is our justice and truth.
Read more at Archdiocese of Washington.