The Eucharistic Advent. Not First or Second, but Sacramental

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Let all mortal flesh keep silence, and with fear and trembling stand; | Ponder nothing earthly-minded, for with Blessing in His Hand | Christ our God to earth descendeth, our full homage to demand.

King of Kings, yet born of Mary, as of old on earth He stood, | Lord of Lords, in Human Vesture—in the Body and the Blood— | He will give to all the Faithful His Own Self for Heavenly Food.

Rank on rank the Host of Heaven spreads its vanguard on the way,

As the Light of Light descendeth from the realms of endless day,

That the Powers of Hell may vanish as the darkness clears away.

At His Feet the six-winged Seraph:  Cherubim with sleepless eye

Veil their faces to the Presence, as with ceaseless Voice they cry—

Alleliua, Alleliua, Alleliua, Lord most High!

     Gerard Moultrie, Lyra eucharistica: hymns and verses on the holy communion, ancient and modern; with other poems, 2nd ed. (London:  Longman, Green, Longman, Roberts, and Green, 1864), 133, following a prose translation of the Cherubic Hymn (τοῦ χερουβικοῦ) of the mid-5th-century-or-earlier Liturgy of St. James by Thomas Rattray (ODCC, 3rd rev. ed.; J. R. Watson in The Canterbury Dictionary of Hymnology).  The Cherubic Hymn appears on p. 176 (Greek)/177 (Latin) of the critical edition in Patrologia orientalis 26 (1950):  119-256, and on pp. 41-42 of Brightman, Liturgies eastern and western (1896), pp. 31-68 (Greek) and 69-110 (Syriac).  I reproduce the Greek and latin here from PO 26, but with italics for Brightman's unical:

Σιγησάτω πᾶσα σάρξ βροτεία καὶ στήτω μετὰ φόβου καὶ τρόμου καὶ μηδὲν γήϊνον ἐν ἑαυτῇ λογιζέσθω· ὁ γὰρ βασιλεὺς τῶν βασιλευόντων, Χριστὸς ὁ θεὸς ἡμῶν, προέρχεται σφαγιασθῆναι καὶ δοθῆναι εἰς Βρῶσιν τοῖς πιστοῖς, προηγοῦνται δὲ τούτου οἱ χοροὶ τῶν ἀγγέλων μετὰ πάσης ἀρχῆς καὶ ἐξουσίας, τὰ πολυόμματα χερουβὶμ καὶ τὰ ἑξαπτέρυγα σεραφὶμ, τὰς ὄψεις καλύπτοντα καὶ βοῶντα τὸν ὕμνον, Ἀλληλούϊα.

Sileat omnis caro mortalis et stet cum timore et tremore neve quidquam terrestre in se meditetur.  Rex enim regnantium, Christus Deus noster, prodit ut mactetur deturque in escam fidelibus, praecedunt autem hunc chori angelorum cum omni principatu et potestate, cherubim multis oculis et seraphim sex alis praedita, facies velantia et vociferantia hymnum, alleluia. 

John Mason Neale, The Liturgies of S. Mark, S. James, S. Clement, S. Chrysostom and the Church of Malabar (1859), 39-40 (31-65):

Let all mortal flesh keep silence, and stand with fear and trembling, and ponder nothing earthly in itself; for the King of Kings and Lord of Lords, Christ our God, cometh forward to be sacrificed and to be given for food to the faithful; and He is preceded by the choirs of the Angels, with every Domination and Power, the many-eyed Cherubim, and the six-winged Seraphim, that cover their faces, and vociferate the hymn, Alleluia, Alleluia, Alleluia.

James Donaldson, ANF 7, as reproduced at newadvent.org:

Let all mortal flesh be silent, and stand with fear and trembling, and meditate nothing earthly within itself:—For the King of kings and Lord of lords, Christ our God, comes forward to be sacrificed, and to be given for food to the faithful; and the bands of angels go before Him with every power and dominion, the many-eyed cherubim, and the six-winged seraphim, covering their faces, and crying aloud the hymn, Alleluia, Alleluia, Alleluia.

The Liturgy of St. James "at Zante (and sometimes elsewhere) on 23 Oct. (acc. to the E. Church, the day of St James's death) and at Jerusalem on the Sunday after Christmas" (ODCC).