O Holy God.
Holy Strong.
Holy Immortal, have mercy on us.
This hymn is extremely ancient, perhaps of
apostolic origin.In the rubrics of the Greek Liturgy, in
which the hymn is said very frequently, it is always referred to as the
Trisagion (tr�s thrice, `�gios holy), and is thus generally and
properly known. The Trisagion is sung in the Greek Church at all the
canonical hours and several times during the long Mass-service.