Genesis 1:3: "And God said, 'Let there be light,' and there was light."
John 1:1-14: "1 In the beginning was the Word, and the Word was with God, and the Word was God. 2 He was in the beginning with God. 3 All things were made through him, and without him was not any thing made that was made. 4 In him was life, and the life was the light of men. 5 The light shines in the darkness, and the darkness has not overcome it. 5 The light shines in the darkness, and the darkness has not overcome it.
"6 There was a man sent from God, whose name was John. 7 He came as a witness, to bear witness about the light, that all might believe through him. 8 He was not the light, but came to bear witness about the light.
"9 The true light, which enlightens everyone, was coming into the world. 10 He was in the world, and the world was made through him, yet the world did not know him. 11 He came to his own, and his own people did not receive him. 12 But to all who did receive him, who believed in his name, he gave the right to become children of God, 13 who were born, not of blood nor of the will of the flesh nor of the will of man, but of God.
"14 And the Word became flesh and dwelt among us, and we have seen his glory, glory as of the only Son from the Father, full of grace and truth."
2 Corinthians 4:6: "For God, who said, 'Let light shine out of darkness,' has shone in our hearts to give the light of the knowledge of the glory of God in the face of Jesus Christ."
1 Peter 2:9: "But you are a chosen race, a royal priesthood, a holy nation, a people for his own possession, that you may proclaim the excellencies of him who called you out of darkness into his marvelous light."
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Broadly speaking, the first verse comes from Genesis 1:3, and the rest of the hymn, continuing the theme of light, draws from the other passages that are cited.
There are, however, a couple uncited passages that the hymn text draws from more heavily. The lines "Thy strong word did cleave the darkness; / At Thy speaking it was done" certainly describe what occurs in Genesis 1:3, but structurally, they more closely resemble Psalm 33:9: "For he spoke, and it came to be; he commanded, and it stood firm."
Most of the second verse ("Lo, on those who dwelt in darkness, / Dark as night and deep as death, / Broke the light of Thy salvation") is taken from Isaiah 9:2: "The people who walked in darkness have seen a great light; those who dwelt in a land of deep darkness, on them has light shined."
