QÉDHÛSÁH. — Trisagion, a liturgical composition inserted into the morning prayer at the moment when the officiating cleric repeats the Sémônêh 'esvêh (v.).
It derives its origins from Is. 6:3 and in its fuller form also includes Ez. 3:12b; Ps. 146:10; Deut. 6:4; Num. 15:41c. In its distant and obscure origins it was recited only on feast days, but over time it came to be used on weekdays as well and after public scriptural readings. The Q. has exercised notable influence upon Christian liturgy.
BIBL.: I. Elbogen, Gesch. des jud. Gottesdienstes, 2nd ed., Frankfurt a.M. 1924, pp. 61–67, 79; M. E. Ieremsky, Kaddisch, in Enc. Jud., IX, cols. 1118–23. On Q. and the Trisagion cf. A. Baumstark, in Jahrbuch für Liturgiewissenschaft, 3 (1923), pp. 18 ff.; E. Peterson, Theologische Traktate, Munich 1951, pp. 333, 344 ff.; 385.