…Next come three short hymns known as the “Antiphons.” In the earliest centuries, these hymns were sung by people as they were on their way to worship, or waiting outside church for the official entrance of the clergy. The hymns (which, despite the name, aren’t necessarily sung antiphonally) are composed of verses from the Psalms or Beatitudes, or offer brief prayers of intercession (such as, “Save us, O Son of God, who rose from the dead”). After the second antiphon we sing a hymn attributed to the emperor Justinian (AD 483–565).
O Only-begotten Son and immortal Word of God,
Who for our salvation willed to become incarnate