Phos Hilaron (“O Gladsome Light” or “Gladdening Light”) is an ancient Christian hymn, likely written in the late 3rd or early 4th century, and has been used at Evening Prayer in most Christian traditions since then.
O gladsome Light,
pure brightness of the everliving Father in heaven,
O Jesus Christ, holy and blessed!
Now as we come to the setting of the sun,
and our eyes behold the vesper light,
we sing your praises, O God: Father, Son, and Holy Spirit.
You are worthy at all times to be praised by happy voices,
O Son of God, O Giver of Life,
and to be glorified through all the worlds.