"begotten before all ages, he has begun to exist in time"

Honthorst, "Adoration" (1620)

"on the feast of this awe-filled mystery, though invisible in his own divine nature, he has appeared visibly in ours; and begotten before all ages, he has begun to exist in time; so that, raising up in himself all that was cast down, he might restore unity to all creation and call straying humanity back to the heavenly Kingdom."

"Qui, in huius venerandi festivitate mysterii, invisibilis in suis, visibilis in nostris apparuit, et ante tempora genitus esse coepit in tempore; ut, in se erigens cuncta deiecta, in integrum restitueret universa, et hominem perditum ad caelestia regna revocaret."

     Preface II for the Nativity of the Lord, newly composed for the Missal of Paul VI on the basis of Sermon 22.2 of St. Leo the Great (trans. Freeland & Conway, FC 93, pp. 81 ff. (80-87); CCSL 138, ed. Chevasse (1973), pp. ; PL 54, cols. 195-196), "of the phrasing" of which there were "already reminiscences . . . in a variety of liturgical texts" reproduced at Anthony Ward and Cuthbert Johnson, The prefaces of the Roman missal:  a source compendium with concordance and indices (Rome:  C.L.V. - Editioni Liturgische, 1989), 76-82.  Previous ICEL "translation," as reproduced on p. 81:

Today you fill our hearts with joy as we recognize in Christ the revelation of your love.  No eye can see his glory as our God, yet now he is seen as one like us.  Christ is your Son before all ages, yet now he is born in time.  He has come to lift up all things to himself, to restore unity to creation, and to lead mankind from exile into your heavenly kingdom.