In the morning service of Matins in the Byzantine Rite, the liturgical poem called the Canon is followed immediately by a Hymn of Light – in Greek, exapostilarion or photogogikon; in Slavonic, svitilen). These hymns are usually “read” or chanted simply by a reader, but for great feasts they have special melodies of their own. (Think “You, King and Lord” at Pascha.)
Music for the Matins hymn of light for the feast of the Nativity on December 25 can be found in the 1925 Prostopinije of Theodore Ratzin, who transcribed the 1906 Bokshai Prostopinije with addition material from the Slavonic Irmologion. Here is a setting in English:
This hymn is sung at Matins on Christmas, and also on the Sunday after the Nativity, when we celebrate the relatives of the Lord: Joseph, his foster-father; James, his cousin and first bishop of Jerusalem, and King David.