Here is Malcolm Guite's sonnet based on the O Antiphon appointed for 21 December in the Sarum practice:
O Rex Gentium
O King of our desire whom we despise,
King of the nations never on the throne,
Unfound foundation, cast-off cornerstone,
Rejected joiner, making many one,
You have no form or beauty for our eyes,
A King who comes to give away his crown,
A King within our rags of flesh and bone.
We pierce the flesh that pierces our disguise,
For we ourselves are found in you alone.
Come to us now and find in us your throne,
O King within the child within the clay,
O hidden King who shapes us in the play
Of all creation. Shape us for the day
Your coming Kingdom comes into its own.
And here is the corresponding portion (ll. 1-17) of Cynewulf’s ‘Christ I’ Advent lyrics. The Old English text can be found in The Exeter Book, ed. George Philip Krapp and Elliott Van Kirk Dobbie, Vol. III of The Anglo-Saxon Poetic Records, A Collective Edition (Morningside Heights, NY: Columbia U, 1961), p. 3. The translation is from Kevin Crossley-Holland, ed. and trans., The Anglo-Saxon World: An Anthology (Oxford: Oxford U, 1984), p. 197. Unfortunately, the opening lines of this poem have been lost, so it begins in media res, as it were.
. . . to the King.
You are the corner-stone the builders
once discarded. It becomes you well
to stand as the head of the great hall,
to lock together the lengthy walls,
the unbreakable flint, in your firm embrace,
so that all things on earth with eyes
may marvel endlessly, O Lord of Glory.
O true, victory-bright One, reveal now your own might
through your mysterious skill, and let wall
remain upright against wall. The hall needs
the care of the Craftsman and the King Himself
to repair—it is decayed now—the house
under its roof. He created the body’s limbs
of clay. Now the Lord of Life must save
dispirited men from devils, the wretched
from damnation, as He has often done before.