The song of praise which the angels sing to God is a common theme in the Jewish and Christian apocalyptic and mystic literature. In his vision Isaiah heard the seraphim uttering (Isa. 6:3) what later became known as the *Kedushah (in Greek Trishagion). The idea of the angels singing in the heavenly spheres is very likely an old one; it is the counterpart of the song which the levites sing in the Temple (e.g., i Chron. 6:16–17). In the apocalyptic literature the seer translated to heaven sees, among other things, the throne of God surrounded by angels singing their perpetual song to God (ii En. 39–40). This part of the vision may be called the mystical core of the apocalyptic experience. The angelic song in the apocalyptic literature is generally a development of Isaiah 6:3 and Ezekiel 3:12. The song of the angels is mentioned often in ii Enoch, where it is revealed to the seer (Version ii 23:2; cf. also Test. Patr., Levi 3:8). Particularly rich in its angelic doxologies, or songs of praise, is the Jewish-Christian Book of Revelation. The Qumran sect had a highly developed angelic liturgy (see Strugnell, in: vt, Supplement, 7 (1959), 318–45).
The heikhalot literature of the Jewish mystics of the talmudic period is replete with angelic songs. Even the throne of God sings a special song to God (Heikhalot Rabbati, 24–26). The angelic songs which the mystic hears are not short doxologies as in the apocalyptic writings, but long lyrical expressions of the divine holiness, appropriately called "numinous hymns" (R. Otto, The Idea of the Holy (1923), 34). There are several references to the angelic song in talmudic and midrashic literature. The two main ideas expressed there are:
(a) the angels do not repeat their song (which is always that of Isa. 6:3 and Ezek. 3:12); when they have finished singing it, they disappear;
(b) there is a special order according to which the angels divide the song among themselves.
There are also differences of opinion as to when the angels sing their song: during the day only (Lam. R. 3:23; Hul. 91b); during the night, when Israel does not pray (Ḥag. 12b; Av. Zar. 3b); or during both day and night (ser 7:34).
H. Bietenhard, Die himmlische Welt im Urchristentum Spaetjudentum (1951), 137ff. (incl. bibl.); G. Scholem, Jewish Gnosticism … (1965), 20–30; Van Unnik, in: Vigiliae Christianae, 5 (1951), 204–48 (Eng.); Flusser, in: Abraham, Unser Vater… Festschrift Otto Michel (1963), 129–52.