(15) To give light.--This was to be henceforward the permanent arrangement for the bestowal of that which is an essential condition for all life, vegetable and animal. As day and night began on the first day, it is evident that very soon there was a concentrating mass of light and heat outside the earth, and as the expanse grew clear its effects must have become more powerful. There was daylight, then, long before the fourth day; but it was only then that the sun and moon became fully formed and constituted as they are at present, and shone regularly and clearly in the bright sky.

1:14-19 In the fourth day's work, the creation of the sun, moon, and stars is accounted for. All these are the works of God. The stars are spoken of as they appear to our eyes, without telling their number, nature, place, size, or motions; for the Scriptures were written, not to gratify curiosity, or make us astronomers, but to lead us to God, and make us saints. The lights of heaven are made to serve him; they do it faithfully, and shine in their season without fail. We are set as lights in this world to serve God; but do we in like manner answer the end of our creation? We do not: our light does not shine before God, as his lights shine before us. We burn our Master's candles, but do not mind our Master's work.And let them be for lights in the firmament of the heaven,.... To continue there as luminous bodies; as enlighteners, as the word signifies, causing light, or as being the instruments of conveying it, particularly to the earth, as follows:

to give light upon the earth; and the inhabitants of it, when formed:

and it was so: these lights were formed and placed in the firmament of the heaven for such uses, and served such purposes as God willed and ordered they should.