‘And God said, “Let there be lights in the firmament of the heaven to separate the day from the night, and let them be for signs and for seasons, for days and years, and let them be for lights in the firmament of the heavens to give light upon the earth”. And it was so.'
From now on periods of light and darkness will be determined by the action of sun and moon. No longer will darkness permanently threaten for it is controlled. It is these lights which will now determine the length of days and years. To ancient man his ideas of time were ruled by the heavenly lights. They were the signs that guided his thoughts on the passage of time. From them he knew the seasons. Days and months and years resulted from their activity. And it was they under God which ensured that permanent, enveloping darkness did not prevail.
They were also the signs to men of God's continued provision for them. While vegetation has been able to grow without these cycles, it will be better for man that these functions are systematised. No more definite statement could be made that before this act days, years and seasons had not existed as we know them. But now those seasons will be the guarantee of the means of existence, and later the rainbow will be God's sign of their permanence for man (Genesis 8:22; Genesis 9:12-17).
Furthermore these lights will give light to the inhabitants of earth. The sun will enable them to go about their daily round. At night the moon will guide the hunter and the shepherd. But the main occurrence and emphasis of the fourth day is that the ‘lights' are called on to establish the times and seasons. Time and provision is systematised and guaranteed.