O Adonai

O Adonai, and Leader of the House of Israel, who appearedst in the bush to Moses in a flame of fire,
and gavest him the Law in Sinai: come and deliver us with an outstretched arm.

​Divine Worship: The Missal

‘[T]he Church in Advent calls upon the coming Christ as “O Adonai”. It is a direct application of the Holy Name, in its covert form, to Mary’s son. One of the earliest Christian faith-formulas was “Jesus is Lord”. “If you confess with your lips that Jesus is Lord and believe in your heart that God raised him from the dead”, wrote St Paul to the Romans, “you will be saved” (10:9). It was the great and sustaining creed of the post-resurrection Church at Pentecost, when the full redeeming significance of Jesus’ name burst forth upon the Christian community like light from heaven, like a terrific fire that burned and yet never consumed. “Know assuredly,” cried the apostle Peter in his Pentecost sermon, “that this Jesus, delivered up according to the definite plan and foreknowledge of God, God has made both Lord and Christ, Leader and Saviour” (Acts 2:23, 36; 5:31). Not by accident was Jesus crucified, nor by the whim of tragic fate, but by deliberate, pre-destined design, in order that sin might be forgiven through the name of Jesus Christ, and the Spirit of that name by poured out and received (Acts 2:38).
 
… The Advent antiphon’s supplication – “O Adonai, you gave the Law on Sinai. O come and save us with your mighty power’ – is not however for the Jewish law or the Mosaic covenant. It is for the reality that these things signified and which came to pass at Christian Pentecost: the new covenant, the new law is now inscribed not on tablets of stone but on human hearts. This was what the prophet Jeremiah had declared would come about in the latter days, in the age of Messiah. “Behold, the days are coming, says the Lord, when I will make a new covenant with the house of Israel and the house of Judah, not like the covenant I made with their fathers when I took them out of Egypt, my covenant which they broke, though I was their husband, says the Lord. But this is the covenant which I will make with the house of Israel after those days, says the Lord: I will put my law within them, and I will write it upon their hearts; and I will be their God and they shall be my people” (31:31-33). The waiting Church of Advent today keeps these words in mind as it imitates the first disciples of the Acts who waited in the upper room for this promise from the Father to appear. Christmas therefore is a type of Pentecost. Men awaiting a birth. The birth of the Lord in a stable. The birth of the Church in an upper room in Jerusalem. The re-birth of hearts in a fiery baptism of the Spirit, God’s “mighty power” sent in response to the prayer, “O come and save us”’. 

from Seven Bells to Bethlehem: The O Antiphons by Fr Oliver Treanor