TRISAGIO. - From the Greek τρεῖς - *ἅγιος*: a hymn in which the word *Sanctus* is repeated three times. A distinction is made between the biblical form and the non-biblical form of turgic origin.
1) The biblical Trisagion or triple *Sanctus* at the end of the Preface is derived from *Is. 6, 3* (cf. *Apoc. 4, 8*), and is therefore also called the “seraphic hymn.” Already in use in the synagogue (cf. the *Keduscha* of the Morning Office), it is found in Clement of Rome (*Ad Corinthios*, chap. 34), in the liturgy of the Apostolic Constitutions, and in all Eastern liturgies beginning with the Euchologion of Serapion, from which it passed into Spain and Gaul (St. Hilary). It is not found in St. Justin or in the *Traditio Apostolica* of Hippolytus of Rome. It entered the Roman liturgy perhaps under Sixtus III (d. 440) from the Syriac liturgy. The liturgical form differs from the biblical one by adding the words *Deus* and *caeli*, while retaining the Hebrew word *sabaoth*. Originally it was sung in common by the priest and the people, then in the Carolingian period by the subdeacons, and now by the choir. It also occurs in the *Te Deum* (q.v.).
2) The Trisagion of liturgical origin, an acclamation or hymn in honor of the Most Holy Trinity, occurs in the Byzantine rite in all offices, and in the other Eastern rites it is used frequently. In the Roman liturgy it is used in the *preces* at Prime, in the *Rituale* (ed. 1952, tit. X, 12) at the procession *in quacumque tribulatione*; it is also found inscribed on bells. It arose, especially with the *Improperia* (q.v.) of Good Friday, between the 9th and 10th centuries, from the Gallican liturgy as a dramatic element in the act of adoration of the Holy Cross; it is sung in Greek with a Latin translation. A simple form and a paraphrase with various additions are distinguished, e.g., “qui crucifixus es pro nobis,” “qui venisti ab excelsis pati pro nobis” (Missal of Bobbio, 25: *dicitur post Aios*), “[Agnus Dei] qui tollis peccata mundi [miserere nobis]” or similar to *Apoc. 4, 10-11*, etc.