The fourth O Antiphon is to the Key of David.
O Clavis David, et sceptrum domus Israel;
qui aperis, et nemo claudit;
claudis, et nemo aperit:
veni, et educ vinctum de domo carceris,
sedentem in tenebris, et umbra mortis.
O Key of David, and scepter of the house of Israel;
who opens, and no one closes;
who closes, and no one opens:
come, and lead the fettered ones out from the prison-house,
those sitting in darkness, and the shadow of death.
Nevertheless, it is also one of the more difficult and obscure of Christ’s traditional titles. The original passage describes a transfer of authority from the master of Hezekiah’s palace to Eliakim, a man of the Lord’s choosing. Isaiah declares, “the key of the house of David will I lay upon his shoulder.” The revelation to St. John states that Christ now possesses this key, and because of this a door that cannot be shut has been set before certain faithful Christians.
This is part of a network of opening/shutting/binding/loosing images in the scriptures. Perhaps the most notable instance, and probably a deliberate reference to Eliakim in Isaiah, is when Jesus promises Peter the keys of his kingdom, that whatever he binds on earth will be bound in heaven, and whatever he looses on earth shall be loosed in heaven. (See also Matthew 23:13 for a negative use of this imagery.)
These examples in mind, we see that the hymnist made a very interesting choice in how he concludes this antiphon. The language of the key, to any early Christian, clearly points to the authority of Christ, in and by whom the Church has power to govern its members and to make binding dogmatic decisions. The scepter is obviously a symbol of rule as well.
But the antiphon draws a line to Christ’s role as liberator. In fact, it seems to imply the image of Revelation 1:18, which depicts the victorious Son as holding “the keys of Death and Hades,” having worked the destruction of the fiend whose is the power of death (Hebrews 2:14-15).
We cannot forget this aspect of Christ’s advent, lest we see our Lord as a kind of arbitrary despot, opening the door for some and closing it for others by terrible decree. We see that Christ has received authority from the Father not for the sake of drawing a line between good people and bad people, but for the heroic purpose of invading the prison of death and robbing the devil of his captives.
This is why the child in the manger descended to earth, and it is why he descended further into Hades. He carries a secret weapon against the reign of darkness in the world, one that will invert the order of death and reverse its effects. O Clavis David celebrates Christ’s mission to free death’s captives. The Christ who entered a mortal womb would one day go down into the very heart of death and trample it down.