Briefly explain the main themes in verse 37 of Surah Fussilat and explain their importance in a Muslim's life?

Themes:
This verse of Surah Fussilat speaks of the day and night and the sun and the moon as the signs of Allah for those who think on the universe. They are not objects of Divine Power but creatures of Allah. How can they be worshiped? The sun and the moon are moving objects that remain on their defined trajectories according to the law of Allah and He is manifesting Himself in their form. Hiding of the sun during night and that of the moon during daytime clearly indicate that they are helpless and powerless creatures. The Quran says, "In the creations of the heavens and the earth and the alteration of Night and Day, surely there are signs for men who understand" (3:190). 


Importance in a Muslim's life:

Prostating before the sun, moon, fire, idols, graves or other created objects is shirk, the most heinous crime and absolutely unforgivable. If someone has minor traces of shirk in his belief, he will never be rewarded Paradise in the Hereafter. He will the fuel of the hell for ever. A human is the most respected creature of Allah. When he bows down before sun or moon, it debases his dignity. His focus moves away from his true Master. If he doesn't repent, he will go astray. Allah will never bestow His Mercy on him in the Hereafter. 


Sun and moon are created merely for the benefits of mankind. The night is created for the rest of the people and the day for earning essentials of the daily life. They are subserviant to their Lord in which there is a lesson of obedience for the transgressors. Some people say that they do not bow down to these objects but bow to God through them. If you really are true worshippers of Allah, there is absolutely no need of these intermediaries. Bow down to Him directly.