This is, for what it's worth, the oldest work I selected for this year's project. It is, in fact, the oldest work of any kind I've ever featured in an Advent project. Incidentally, most translations of this work credit it to the Anglo-Saxon poet Cynewulf, but it is now believed that it was not written by him. Shame on him for trying to take credit for it!
This passage may be of particular interest to fans of J.R.R. Tolkein. Here are the first two lines in Old English: "Eálá Earendel engla beorhtast / Ofer middangeard monnum sended." In modern English: "Hail Earendel brightest of angels, / over Middle Earth sent to men." Tolkein used those lines as the basis for his character Eärendil, a mariner who carries the morning star across the sky. His story is told in The Silmarillion, and his name comes up several times in The Lord of the Rings.
From Christ I
Hail Day-Star! Brightest angel
sent to man throughout the earth, and
Thou steadfast splendour of the sun,
bright above stars! Ever Thou
illumine with Thy light the time of every season.
As Thou, begotten God of God,
Son of the True Father,
Without beginning abodeth ever in the splendour of heaven,
so now for need Thy handiwork
beseecheth boldly that Thou send
the bright sun unto us; that Thou
come and shed Thy light on those who long ere this,
compassed about with mist and in the darkness,
clothed in sin, sit here in the long night,
and must needs endure the dark shadow of Death.
Now we are full of hope and put our trust in Thy salvation,
heralded to the hosts of men by the word of God,
which in the beginning was with God,
with the Almighty Father co-eternal, and afterward was made
flesh unstained of sin, which the Virgin bare,
a solace unto wretched men. God was seen among us
without sin; together dwelt
the mighty Son of God and the son of man,
in peace among the people. Wherefore we may rightfully
give thanks forever to out Victor-Lord,
that He would send Himself to us.
Author unknown (8th or 9th century)
Translated by Charles W. Kennedy (1882–1969)