The 'O Antiphons' (an antiphon is a spoken response in a church service) have been used in liturgical Christian traditions since as far back as the sixth century. They are spoken before reading the Magnificat at Evening Prayer during the last seven days of Advent.
My thanks to Malcolm Guite for these poetic reflections. Here is the one for 20th December: O Clavis David – O 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.
Detail from an earthenware Passover plate, Spain, c.1480 ISRAEL MUSEUM/NAHUM SLAPAK O Key of David and sceptre of the House of Israel;
you open and no one can shut;
you shut and no one can open:
Come and lead the prisoners from the prison house,
those who dwell in darkness and the shadow of death
Even in the darkness where I sit
And huddle in the midst of misery
I can remember freedom, but forget
That every lock must answer to a key,
That each dark clasp, sharp and intricate,
Must find a counter-clasp to meet its guard,
Particular, exact and intimate,
The clutch and catch that meshes with its ward.
I cry out for the key I threw away
That turned and over turned with certain touch
And with the lovely lifting of a latch
Opened my darkness to the light of day.
O come again, come quickly, set me free
Cut to the quick to fit, the master key.