KJV Matthew 5: 14 Ye are the light of the world. A city that is set on an hill cannot be hid. 15 Neither do men light a candle, and put it under a bushel, but on a candlestick; and it giveth light unto all that are in the house. 16 Let your light so shine before men, that they may see your good works, and glorify your Father which is in heaven.
Luther used the sun and the moon to compare the Gospel with the Law, since the energy of the sun is needed for the moon to illuminate the night sky. In the same way, the light of Christ is in those who believe in Him and absent in those who do not. Even the smallest light can be seen in complete darkness. In fact, utter darkness makes light especially important for believers and unbelievers alike.
President Ronald Reagan’s farewell speech included this Biblical reference:
“In my mind it was a tall, proud city built on rocks stronger than oceans, windswept, God-blessed, and teeming with people of all kinds living in harmony and peace; a city with free ports that hummed with commerce and creativity. And if there had to be city walls, the walls had doors and the doors were open to anyone with the will and the heart to get here.”
No one can hide a city built up high on a hill or mountain. The light of that city penetrates the darkness and draws people to it. In contrast, darkness makes people afraid, and they stumble from the smallest obstacle. When my brother lost his shoe in a sheep pen at night, we were playing with the farmer’s children. No one knew how to find it in the muck – until the farmer brought out his flashlight, laughing. The farmer did not hide the light but shone it until the shoe was found and extracted with the expected jokes.
The secondary light from the Light of the World shines in us as we practice the forgiveness which bears fruit in love. Most importantly, that begins with our own households, where faith, forgiveness, and grace dissolve the darkness of our natural selves and selfishness. The early Christian martyrs witnessed to their faith by dying instead of silencing themselves and hiding the truth. They were honored to model the Savior and in doing so spread the Gospel. John Hus’ death as a martyr paved the way for Luther stating “We are all Hussites” and the Reformation changing Europe and the world.
The light does not remain within the household but spreads so that all people will have the chance to see the meaning of the true Christ, the Savior of the World.
 https://ourlostfounding.com/ronald-reagan-and-the-shining-city-upon-a-hill/#:~:text=He%20said%2C%20%E2%80%9CFor%20we%20must,%2Dword%20through%20the%20world.%E2%80%9D. See also John Winthrop Dreams of a City on a Hill, 1630.