"Let us bless the Father, and the Son, with the Holy Spirit. Let us praise and exalt him above all forever."

Einsiedeln, Stiftsbibliothek,
Codex 121, 312 (960-970)

"Benedicamus Patrem et Filium cum Sancto Spiritu; laudemus et superexaltemus eum in saecula."

     I haven't looked for scholarship on the first appearance of this, though according to CANTUS it is present in manuscripts dated to the 10th century:  CH-E 121 to 960/970, and F-Pnm lat. 1085 to the last quarter.

Dan 3:52 | Prayer of Azariah and Song of the Three Young Men 29 (I think that's the verse on which this is based, though I haven't examined the whole chapter closely):

Εὐλογητὸς εἶ, κύριε ὁ θεὸς τῶν πατέρων ἡμῶν, καὶ αἰνετὸς καὶ ὑπερυψούμενος εἰς τοὺς αἰῶνας, καὶ εὐλογημένον τὸ ὄνομα τῆς δόξης σου τὸ ἅγιον καὶ ὑπεραινετὸν καὶ ὑπερυψωμένον εἰς πάντας τοὺς αἰῶνας.

benedictus es Domine Deus patrum nostrorum et laudabilis et superexaltatus in saecula et benedictum nomen gloriae tuae sanctum et laudabile et superexaltatum in omnibus saeculis.