GENESIS 1:15
 

and let them be for lights in the firmament of the heavens to give light on the earth”; and it was so. [Genesis 1:15 NKJV]
 

And let them serve as lights in the expanse of the sky to shine upon the earth.” And it was so. [Genesis 1:15 BSB]

Commentaries:

This is the Word of God that made the Lights there (in heaven) to give light on earth. So much Lights have been in heaven, but none was on earth and none gave light on earth until this Word of God Commanded these Lights to give light on earth. When the Word said, "Let there be light," 'there was light but it was not giving light on earth. And when the Word said, "Let Lights be there (in firmament of heaven)," the same Word had to specify saying, "and let those Lights be for lights or serve as Lights in order to give light on earth."
 

When God said, let there be light, there was light but the light was not serving as light or being for light on earth: rather that light served as day (time). Also these Lights in the Firmament of heaven were by default going to be for or serve as signs, seasons, days and years, etc, until this Word of God above added that they should also be for lights or serve as lights to give light on earth. To give light on earth was what qualifies them to shine on earth. To shine means to give light, not to take it. Many people think they are shining because they are getting or receiving praises and things from other people. But shining is not in what you are receiving, but rather shining is in what you are giving out as lights.

Bible Teacher:

Their far locations in the firmament of the heavens will not prevent their lights, glories, signs, inspirations or revelations, from reaching those on earth. Basically, when they are faithful lights in the firmament of heaven, their light will also reach the worlds on the earth. Some Lights can both light up heavens and earth. 
 

If you are being a great faithful light or star in heaven, you need no worry for your light to reach on earth. Those on earth will later see and celebrate your light so long as you keep your domain in the realms of heaven, and you fulfill your high calling (God's ordained roles for you) in the high heavens. The higher you go above and the more committed and faithful you are to your appointment and ordination above, the more you give light both in heaven and on earth. There's no servant of God who is a great light or star (celebrity) in heaven above and among the angels of God, that would not eventually become a known lightbearer and celebrated star on earth when the Kingdom of Heaven prevails over all the earth. If you be great in heaven, you shall also be great on earth. The fame and reputations in heaven above shall swallow the fame and reputations on earth.
 

Therefore, do not strive to be the light on earth when you are not a light in heaven above; rather seek first the Kingdom of God and how to become a great shining light above in heaven, and then it will eventually be done on earth as it is in heaven. Let your city be set up on a hill (heaven), and then the city set on the hill shall not be hidden.

Commentaries:

A man trying to become a light on earth without he first being a light in heaven is likened to a man who lights his candle but puts it under a strong covering, and such light gets covered or swallowed by darkness.
 

But a person who has first become a shining and burning light in heaven is likened to a conspicuous city on a hill that can not be hidden to men.

Bible Teacher:

The same lights ordained as administrators and watchers of times and their differences, are still going to also minister or give light on earth across the firmament of the heavens through thousands of light-years to reach the earth.
 

±±± The primary assignments of those lights [distinguishing between day and night, between days, years, signs and seasons], will not deprive their duty as light to give light on earth.
 

±±± Their duties of revealing hidden times and their differences, now also include their duties of revealing hidden things and their differences.