October 23 is the feast day of Saint James of Jerusalem, also called James the Just, a different James from the one we marked on July 25. This James (though accounts vary) was apparently the brother of Jesus and eventually made bishop of Jerusalem.
On this day many Orthodox churches celebrate the Liturgy of St. James, which is considered to be the oldest liturgy still in regular use. There is some dispute over just how old it is; some say it dates back to 60 A.D., others say that it comes from the late fourth or early fifth century. Some branches of the Orthodox church celebrate this liturgy regularly, not just in commemoration of today's St. James.
If you follow the text of the liturgy online, about a third of the way down the page you may encounter some familiar language that reminds you of the following hymn.
Let all mortal flesh keep silence,
And with fear and trembling stand;
Ponder nothing earthly minded,
For with blessing in thy hand,
Thou, our God, to earth descendest,
Our full homage to demand.
Rank on rank the host of heaven
Spreads its vanguard on the way,
As the Light of light descendeth
From the realms of endless day,
That the powers of hell may vanish
As the angels clear the way.
At thy feet the six-wingèd seraph,
Cherubim with sleepless eye,
Veil their faces to thy presence,
As with ceaseless voice they cry:
Alleluia, Lord Most High!
Liturgy of St. James; adapt. Gerard Moultrie, 1864; alt.
Tune: PICARDY (126.96.36.199.8.7.)
Traditional French melody, 17th c;
adapt R. Vaughan Williams and others
The Cherubic Hymn of the Liturgy of St. James, spoken or sung as the presider brings the gifts to the altar, was adapted into a metrical hymn text by Gerard Moultrie in 1864. It was first matched to the French tune PICARDY by Ralph Vaughan Williams in The English Hymnal of 1906, and has been harmonized by a number of different people since then.