Genesis 1:3

The world came into being by God’s word (cf. Psalms 33:9; Hebrews 11:3). Each of the six creative days began with God speaking. God’s ten pronouncements in this chapter anticipate His ten commandments at Mt. Sinai (Exodus 20:2-17). All but one of Jesus Christ’s miracles occurred immediately after He spoke. The exception occurs in Luke 8:25 when He laid His hands on a blind man. Jesus Christ, the Word of God, was the Creator (John 1:3). The theme of God’s word (spoken, written, or incarnate) continues through the Bible. His word is consistently powerful, as here. Fiat (the Latin word for "Let there be") creation means creation that came into being by God’s word.

"The idea of creation by the word preserves first of all the most radical essential distinction between Creator and creature. Creation cannot be even remotely considered an emanation from God . . . but is rather a product of his personal will." [Note: Gerhard von Rad, Genesis, pp. 51-52.]

The "light" might not have been sunlight (cf. Genesis 1:14). Perhaps it came from a source fixed at a distance from the earth such as the shekinah, the light that manifests God’s glory (cf. Revelation 22:5). [Note: Hamilton, p. 121.] Perhaps God created the sun on the first day, but it became visible on the fourth day. [Note: Sailhamer, "Genesis," p. 26.] A third view is that God created the sun, moon, and stars on the first day and assigned them their specific functions on the fourth day (cf. Genesis 1:14-18). [Note: Ibid., pp. 33-34.]