The third O Antiphon is to the Root of Jesse.
O Radix Jesse, qui stas in signum populorum,
super quem continebunt reges os suum,
quem Gentes deprecabuntur:
veni ad liberandum nos, jam noli tardare.
O Root of Jesse, who stands as an ensign of the peoples,
before whom kings will shut their mouths,
whom the nations will entreat,
come to free us, refuse now to be hindered.
This antiphon hails Christ as the Root of Jesse. This time, it is not Christ’s divinity that is on display, but his messiahship. The great Wisdom of the Cosmos and Lord of Israel is shown as member and head of the royal house of David.
The first line of this antiphon is drawn from Isaiah 11:10, the second from Isaiah 52:15. Isaiah 11 depicts the “root of Jesse” flowering again; the House of David, whose degraded descendants would lose the throne within two centuries, would produce an heir on whom rested the Divine Spirit. This anointed king would rule with justice and turn Zion into a new Eden, and all the Gentiles would be drawn to him out of their own sin and desolation.
This title is an essentially human one, but not at odds with the previous portraits of his transcendent divinity. These successive antiphons embody the orthodox doctrine that Christ is wholly God and wholly Man. The Son, in assuming humanity, became a part of the same genetic House of David that he elected. Again, we see that the Son in the incarnation has come to inhabit the house he prepared through time. Millennia of longing for the divine were finally answered in a form that could be touched and seen.
The second O Antiphon is to Adonai (Lord).
O Adonai, et dux domus Israel,
qui Moysi in igne flammae rubi apparuisti,
et ei in Sina legem dedisti:
veni ad redimendum nos in brachio extento.
O Lord, and leader of the house of Israel,
who appeared to Moses in the fire of the burning bush,
and gave him the Law on Sinai:
come to ransom us with outstretched arm.
In this antiphon, Christ is addressed as God of Israel, the Old Testament Adonai himself. Like the previous antiphon, it depicts Christ in his divinity.
But whereas the mystery of Christ Sophia is manifest in all creation, Christ Adonai is revealed in history. Christ Adonai is the Son in the unity of the Godhead, but also the particular god of Israel, shepherd of his people, lord and lawgiver. He is He-Who-Is, YHWH, and one whose “outstretched arm” is mighty to redeem.
This antiphon celebrates the second stage of revelation, when the source of all being gave Israel his name in the burning bush, and the Law in a cloud of glory on Sinai.
The O Antiphons comprise a liturgical chain of ancient Latin Christian poetry. Their purpose is to tell us who is incarnate as we prepare for the feast of Christ’s birth. They are rich with the messianic imagery of the scriptures, each structured around a title of Christ, respectively, Wisdom, Adonai, Root of Jesse, Key of David, Rising Dawn, King of Nations, and Emmanuel.
We do not know exactly how old these antiphons are, but the evidence suggests sixth century at the latest, and quite possibly earlier. In the Western Church, they are still used at vespers with the Magnificat for the last seven days of Advent (December 17-23, though many Anglicans follow the English tradition of using an eighth antiphon to the Virgin on the 23rd, and thus start a day early). The Christmas hymn, O Come, O Come Emmanuel is an adaptation of the whole set.
I believe these antiphons present us with a complete orthodox Christology. I believe they also image a kind of cosmic descent, illuminating various aspects of the mystery of the incarnation. Meditating on the O Antiphons may be helpful in preparing to celebrate the coming of our Lord.