Genesis 1:3 (ESV)

3 And God said, “Let there be light,” and there was light.

God begins to bring about order for the earth and the whole universe. He first created the light. Everything was dark; then when the Lord says, Let there be light, the light appears. All of a sudden, it is there. We read of this in Psalm 33:8–9, “Let all the earth fear the Lord; let all the inhabitants of the world stand in awe of him! For he spoke, and it came to be; he commanded, and it stood firm.”

The voice of the Lord is mighty (see also Psalm 29:1–11). The Lord is the Almighty for whom nothing is too great or too difficult. He can do and he also does anything he wills. He alone works miracles (see e.g., Genesis 18:14; Exodus 15:11; Psalm 86:9–10; Jeremiah 32:17; Luke 1:37).

The Lord creates the light by his voice, by his command, in a moment. The special thing here is that the light does not yet come from the sun, moon, and stars. God creates these on the fourth day. So what were the source of light for the first three days? God was the One who illuminated the earth for those first days with his glory, his omnipotence. He does not need the sun, moon, and stars to give light on earth. The specific creation of light is his decision. It is not that the Lord depends on the light bearers for light. The only living God is so great and holy that he himself dwells in an inaccessible light. He can give light independently of the light bearers (which he himself creates), see 1 Timothy 6:16. When the Lord Jesus returns and the new heaven and earth will be there, it will again be such that God’s glory will provide the light. Indeed, we read of the New Jerusalem in Revelation 21:23, And the city has no need of sun or moon to shine on it, for the glory of God gives it light, and its lamp is the Lamb. This is also promised in the Old Testament; see Isaiah 60:19