1. Antiquity.

The Trisagion from Isa 6:3 (Heb. Qedusha, Q ) appears in three places in the synagogal liturgy (VII; see also Worship: II, 3), sometimes in combination with Ezek 3:12 and Ps 146:10: (1) as an interpolation in the third benediction of the ʿAmida (Q. ha-ʿAmida), (2) in the first benediction of the Shemaʿ (Q. ha-Yotser), and (3) after the weekly portion (Q. de-Sidra). The origin and relative age of the individual forms of the Qedusha are disputed; its absence in the liturgical texts from Qumran is…