Who, being, etc. The participle ᾢν—not γενόμενος, as in Hebrews 1:4—denotes (as does still more forcibly ὐπάρχων in the cognate passage, Philippians 2:6) what the Son is in himself essentially and independently of his manifestation in time.
This transcendent idea is conveyed by two metaphorical expressions, differing in the metaphors used, but concurrent in meaning. The brightness of his glory. The word δόξα (translated "glory"), though net in classical Greek carrying with it the idea of light, is used in the LXX.
for the Hebrew דוֹבךָּ, which denotes the splendor surrounding God; manifested on Mount Sinai, in the holy of holies, in the visions of Ezekiel, etc; and regarded as existing eternally "above the heavens" (cf.
Exodus 24:15; Exodus 40:34; 1 Kings 8:11; Ezekiel 8:4; Psalms 24:7, Psalms 24:8, etc). But the full blaze of this glory, accompanying" the face" of God, even Moses was not allowed to see; for no man could see him and live.
Moses was hidden in a cleft of the rock while the God's glory passed by, and saw only its outskirts, i.e. the radiance left behind after it; had passed; hearing meanwhile a proclamation of the moral attributes of Deity, by a perception of which he might best see God (Exodus 33:18, etc).
Similarly in the New Testament. There also, as on Sinai, in the tabernacle, and in prophetic vision, the glory of God is occasionally manifested under the form of an unearthly radiance; as in the vision of the shepherds (Luke 2:9), the Transfiguration (Luke 9:28, etc), the ecstasy of Stephen (Acts 7:55).
But in itself, as it surrounds "the face" of God, it is still invisible and unapproachable; cf. John 1:18, "No man hath seen God at any time;" 1 John 1:5, "God is Light;" 1 Timothy 6:16, "Dwelling in the light which no man can approach unto ( φῶς απρόσιτον), whom no man hath seen nor can see."
It denotes really, under the image of eternal, self-existent, unapproachable light, the ineffable Divine perfection, the essence of Deity, which is beyond human ken. "Sempiterna ejus virtus et divinitas" (Bengel).
Of this glory the SON is the ἀπαύγασμα—a word not occurring elsewhere in the New Testament, but used by the Alexandrian writers. The verb ἀπαυγάζω means "to radiate," "to beam forth brightness;" and ἀπαύγασμα, according to the proper meaning of nouns so formed, should mean the brightness beamed forth—this rather than its reflection from another object, as the sun's light is reflected from a cloud.
So the noun is used in Wis. 7:26, as applied to σοφία, which is there personified in a manner suggestive of the doctrine of the λόγος: ἀτμὶς γὰρ ἐστὶ τῆς τοῦ θεοῦ δυνάμεως καὶ ἀπόρροια τῆς τοῦ παντοκράτορος δόξης εἰλικρινής … a̓παύγασμα γὰρ ἐστὶ φωτὸς αἰδίου And Philo speaks of the breath of life breathed lute man (Genesis 2:7) as τῆς μακαρίας καὶ τρισμακαρίας φύσευς απαύγασμα ('De Spec.
Leg.,' § 11). As, then, the eradiated brightness is to the source of light, so is the SON, in his eternal being, to the Father. It is, so to speak, begotten of the source, and of one substance with it, and yet distinguishable from it; being that through which its glory is made manifest, and through which it enlightens all things.
The Person of the Son is thus represented, not as of one apart from God, irradiated by his glory, but as himself the sheen of his glory; cf. John 1:14, "We beheld his glory, the glory as of the only begotten of the Father;" also John 1:4; John 1:9.
The above is the view taken by the Fathers generally, and expressed in the Church's Creed, φῶς ἐκ φωτός. And express Image of his substance; not "of his person," as in the A.V. The latter rendering is due to the long-accepted theological use of the word ὑπόστασις in the sense of personal subsistence, as applied to each of the Three in One.
What the Latins called persona the Greeks at length agreed to call hypostasis, while the Greek οὐσία (equivalent to essentia) and the Latin substantia (though the latter word etymologically corresponds with hypostasis) were used as equivalents in meaning.
But it was long after the apostolic age that this scientific use of the word became fixed. After as well as before the Nicene Council usia was sometimes used to denote what we mean by person, and hypostasis to denote what we mean by the substance of the Godhead; and hence came misunderstandings during the Arian controversy.
Bull ('Def. Fid. Nic.,' 2.9. 11) gives a catena of instances of this uncertain usage. The definite doctrine of the Trinity, though apparent in the New Testament, had not as yet come under discussion at the time of the writing of this Epistle, or been as yet scientifically formulated; and hence we must take the word in its general and original sense, the same as that now attached to its etymological equivalent, substantia.