“...by the first expression here used, “The brightness of glory,” the apostle intends to set forth unto us the relation of the Son to the Father by an allusion unto the sun and its beams, or the light of fire in iron, some relief may thence be given unto our weak understandings in the contemplation of this mystery, if we observe that one known rule, whose use Chrysostom urgeth in this place, namely, that in the use of such allusions every thing of imperfection is to be removed, in their application unto God. A few instances we may give unto this purpose, holding ourselves unto an allusion to the sun and its beams.
1. As the sun in comparison of the beam is of itself and the beam of the sun; so is the Father of himself, and the Son of the Father.
2. As the sun, without diminution or partition of its substance, without change or alteration in its nature, produceth the beam; so is the Son begotten of the Father.
3. As the sun in order of nature is before the beam, but in time both are co-existent; so is the Father in order of nature before the Son, though in existence both co-eternal.
4. As the beam is distinct from the sun, so that the sun is not the beam, and the beam is not the sun; so is it between the Father and the Son.
5. As the beam is never separate from the sun, nor can the sun be without the beam, no more can the Son be from the Father, nor was the Father ever without the Son.
6. As the sun cannot be seen but by the beam, no more can the Father but in and by the Son.
From Hebrews, Volume 3, Banner of Truth, 92.