Verses 17, 18. - And God set (literally, gave) them (i.e. sun, moon, and stars) in the firmament of the heaven to give light upon the earth, and to rule over the day and ever the night, and to divide the light from the darkness. An intimation that on this day the astronomical arrangements for the illumination of the globe and the measurement of time were permanently settled. And God saw that it was good. Laplace was inclined to question the Divine verdict with regard at least to the moon, which he thought might have been so placed as to be always full, whereas, at its present distance from the earth, we are sometimes deprived of both its light and the sun's together. But not to dwell upon the fact that to remove the moon four times its present distance from the earth, which it would require to be in order to be always full, would necessitate important changes in the other members of the solar system which might not be for the earth's advantage, the immediate effect of such a disposition of the lunar orb would be to give us a moon of only one sixteenth the size of that which now dispenses its silver beams upon our darkened globe (Job 11:12).

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 God set them in the firmament of the heaven,.... He not only ordered that there they should be, and made them that there they might be, but he placed them there with his own hands; and they are placed, particularly the sun, at such a particular distance as to be beneficial and not hurtful: had it been set nearer to the earth, its heat would have been intolerable; and had it been further off it would have been of no use; in the one case we should have been scorched with its heat, and in the other been frozen up for the want of it. The various expressions used seem to be designed on purpose to guard against and expose the vanity of the worship of the sun and moon; which being visible, and of such great influence and usefulness to the earth, were the first the Heathens paid adoration to, and was as early as the times of Job, Job 31:26 and yet these were but creatures made by God, his servants and agents under him, and therefore to worship them was to serve the creature besides the Creator,

To give light upon the earth; this is repeated from Genesis 1:15 to show the end for which they were made, and set up, and the use they were to be of to the earth; being hung up like so many lamps or chandeliers, to contain and send forth light unto the earth, to the inhabitants of it, that they may see to walk and work by, and do all the business of life, as well as be warmed and comforted thereby, and the earth made fertile to bring forth its precious fruits for the use of creatures in it: and it is marvellous that such light should be emitted from the sun, when it is at such a vast distance from the earth, and should reach it in so short a space. A modern astronomer (m) observes, that a bullet discharged from a cannon would be near twenty five years, before it could finish its journey from the sun to the earth: and yet the rays of light reach the earth in seven minutes and a half, and are said to pass ten millions of miles in a minute.

(m) Huygen. Cosmotheoros. l. 2. p. 125.