Genesis 1:5
3 God said, “Let there be light.” And there was light! 4 God saw that the light was good, so God separated the light from the darkness. 5 God called the light “day” and the darkness “night.” There was evening, and there was morning, marking the first day. 6 God said, “Let there be an expanse in the midst of the waters and let it separate water from water.” 7 So God made the expanse and separated the water under the expanse from the water above it. It was so.
Psalm 74:16
14 You crushed the heads of Leviathan; you fed him to the people who live along the coast. 15 You broke open the spring and the stream; you dried up perpetually flowing rivers. 16 You established the cycle of day and night; you put the moon and sun in place. 17 You set up all the boundaries of the earth; you created the cycle of summer and winter. 18 Remember how the enemy hurls insults, O Lord, and how a foolish nation blasphemes your name.
Notes and References
"... 'light, lamp' is always used in the Pentateuch to designate the sanctuary lamp in the tabernacle: only two other passages, Ezekiel 32:8; Psalm 74:16 use it of the heavenly lights. 'To divide the day from the night'; compare verse 18b, 'the light from the darkness.' Astronomical knowledge makes it difficult to conceive of the existence of day and night before the creation of the sun, but Cassuto argues that the Hebrews did not make an absolute connection between daylight and the sun. At dusk and dawn the world is light even though the sun is below the horizon. This verse, though, affirms the relationship between sun and daylight for all time from the creation of the sun on the fourth day. It must therefore be supposed that the first three days were seen as different: then light and darkness alternated at God‘s behest ..."
Wenham, Gordon J. Word Biblical Commentary: Genesis 1-15 (p. 62) Word Books, 1987