The brightness really refers to the Glory of The New Covenant
(Doxa - glory, splendour, brightness)
2 Corinthians 3:7 But if the ministration of death, written and engraven in stones, was glorious, so that the children of Israel could not stedfastly behold the face of Moses for the glory of his countenance; which glory was to be done away:8 How shall not the ministration of the spirit be rather glorious?
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14 But their minds were blinded: for until this day remaineth the same vail untaken away in the reading of the old testament; which vail is done away in Christ.15 But even unto this day, when Moses is read, the vail is upon their heart.16 Nevertheless when it shall turn to the Lord, the vail shall be taken away.
(Doxa - glory, splendour, brightness)
2 Corinthians 3:7 But if the ministration of death, written and engraven in stones, was glorious, so that the children of Israel could not stedfastly behold the face of Moses for the glory of his countenance; which glory was to be done away:8 How shall not the ministration of the spirit be rather glorious?
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14 But their minds were blinded: for until this day remaineth the same vail untaken away in the reading of the old testament; which vail is done away in Christ.15 But even unto this day, when Moses is read, the vail is upon their heart.16 Nevertheless when it shall turn to the Lord, the vail shall be taken away.