Phos Hilaron — Greek vesper hymn (Gladsome Light)

The most ancient vesper hymn of the Catholic Church known outside Sacred Scripture: composed in Greek in the second or third century, it is already cited as «ancient» by St Basil the Great († 379) in the Treatise on the Holy Spirit (n. 73), who attests it as present on the lips of the Christian people as a traditional hymn received from the fathers. It was chanted at Vespers, when the lamps of the Lychnikón were lit (the ceremony of the evening light): seeing the light of the lamps, the community greets Christ, gladsome light of the glory of the immortal Father. It continues to be the central vesper hymn of the Eastern Catholic Churches of the Byzantine rite, and was incorporated into the new Liturgy of the Hours (1971) as a hymn of Vespers for certain octaves.

Greek original (3rd c., attested by St Basil):

Φῶς ἱλαρὸν ἁγίας δόξης
ἀθανάτου Πατρός,
οὐρανίου, ἁγίου, μάκαρος,
Ἰησοῦ Χριστέ,

ἐλθόντες ἐπὶ τὴν ἡλίου δύσιν,
ἰδόντες φῶς ἑσπερινόν,
ὑμνοῦμεν Πατέρα, Υἱόν,
καὶ ἅγιον Πνεῦμα, Θεόν.

Ἄξιόν σε ἐν πᾶσι καιροῖς
ὑμνεῖσθαι φωναῖς αἰσίαις,
Υἱὲ Θεοῦ, ζωὴν ὁ διδούς·
διὸ ὁ κόσμος σὲ δοξάζει.

English (literal translation from the Greek):

O Gladsome Light of the holy glory
of the immortal Father,
heavenly, holy, blessed,
O Jesus Christ!

Having come to the setting of the sun,
beholding the evening light,
we hymn the Father, the Son,
and the Holy Spirit, God.

It is meet at all times
that thou shouldst be hymned with auspicious voices,
O Son of God, giver of life:
therefore the world doth glorify thee.