A.T. Robertson Commentary 2 Corinthians 4:6

"Seeing it is God, that said, Light shall shine out of darkness, who shined in our hearts, to give the light of the knowledge of the glory of God in the face of Jesus Christ." — 2 Corinthians 4:6 (ASV)

God who said (ο θεος ο ειπων). Paraphrase of Ge 1:3.

Who shined (ος ελαμψεν). Like a lamp in the heart (cf. Matthew 5:15). Miners carry a lamp on the forehead, Christians carry one in their hearts lit by the Spirit of God.

To give the light (προς φωτισμον). For the illumination.

In the face of Jesus Christ (εν προσωπω Ιησου Χριστου). The Christian who looks on the face of Jesus Christ as Moses looked upon the glory of God will be able to give the illumination of the knowledge of the glory of God. See 2:10 for προσωπον.