At Vespers on these days, we pray one of the "O" antiphons at the Magnificat. Today, December 18, the antiphon is "O Adonai":
O Adonái et Dux domus Israël, qui Móysi in igne flammæ rubi apparuisti, et ei in Sina legem dedísti: veni ad redimendum nos in bráchio extento.
O Adonai, and leader of the house of Israel, who appeared to Moses in the fire of the burning bush and gave him the Law of Sinai, come, with outstretched arm, to redeem us.
From "Liturgical Meditations for the Entire Year" by the Sisters of St. Dominic, Adrian, MI (B. Herder, 1960):
Today the Church bids her children, sons of a new and glorious Israel, look back to that time when God Himself came in fiery vision to Moses that He might lead the chosen people from teh slavery of Egypt to the Promised Land. The Red Sea through which they passed to their salvation is compared in the liturgy to the sacrament of baptism through whose saving waters we have reached the state of grace and the hope of life eternal.
As wonderfully as He led the Israelites through the waters of the Red Sea, God led us by His divine providence to the font of baptism. Moses expressed his appreciation of God's goodness in a magnificent canticle of praise. Do we manifest in our lives the gratitude we owe to God for the grace of baptism which brought us "out of darkness into His marvelous light"? (1 Peter 2:9) We should not let this holy season pass without an increased appreciation of the gift of faith which makes our Christmas so different from the empty celebration of those who know not God.