When it is said
Sung at the Divine Liturgy just after Communion.
Once everyone has received, the priest blesses the people with “O God, save Your people and bless Your inheritance”, and the choir answers with this hymn.
On a feast of the Lord the feast’s own hymn takes its place, and in the weeks after Pascha (Easter) “Christ is risen” does.
Where it comes from
No author known
A hymn of Pentecost
It is one of the hymns of Pentecost, the feast of the Holy Spirit, and is sung at Vespers (the evening service) for the feast. The Russian liturgy scholar Alexei Dmitrievsky found it among the Pentecost hymns in service books of the 1100s, and noted how well its words fit the feast.
The Pentecostarion, Vespers of Pentecost, on the Greek Orthodox Archdiocese of America’s liturgical texts site (in Greek); Alexei Dmitrievsky, On the sticheron “We have seen the true Light” in the Liturgies (1886, in Russian)
How it came to follow Communion
Dmitrievsky found that Russian service books first print it after Communion in the 1600s. Before then the clergy answered the priest’s blessing with the Greek words for “Many years, master”. The Pentecost hymn was borrowed to fill that moment. In that place it is much younger than “Let our mouths be filled”, which follows it.
Alexei Dmitrievsky, On the sticheron “We have seen the true Light” in the Liturgies (1886, in Russian); Robert Taft, “The Evolution of the Byzantine Divine Liturgy”
The Scripture in it
The true Light, Who gives light to everyone, was coming into the world.
Peter replied, “Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins, and you will receive the gift of the Holy Spirit.”
Bible text: Berean Standard Bible, public domain.
In Greek
Εἴδομεν τὸ Φῶς τὸ ἀληθινόν, ἐλάβομεν Πνεῦμα ἐπουράνιον,
εὕρομεν πίστιν ἀληθῆ, ἀδιαίρετον Τριάδα προσκυνοῦντες·
αὕτη γὰρ ἡμᾶς ἔσωσεν.