¿What is light?
It is according to the basic and best known definition the light is:
It is the form of energy that allows us to see what surrounds us. It is all electromagnetic radiation that propagates in waveforms in any space, it is capable of traveling through the vacuum at a speed of approximately 300,000 kilometers per second.
One of our greatest sources of light necessary for life is a star that we know as the sun. Then taking this into account.
¿What is our greatest source of spiritual light?
The most obvious answer for me is our father and creator, called God or Jehovah who illuminates our path, who will be our sun when the day is cloudy.
God will guide our way in the darkest and coldest days, so we should not fear in the darkest night, because our God will enlighten us the way and take care of us as a lion. As the previous definition says, our creator allows us to see those around us, he guards us and he propagates in any space in which we find ourselves, that is why we are called "children of light".
Because written is:
Jesus spoke to them again, saying: I am the light of the world; he who follows me will not walk in darkness, but will have the light of life. John 8:12.
I am the LORD, in justice I have called you; I will hold you by the hand and watch over you, and I will make you a covenant for the people, a light for the nations. Isaiah 42: 6
Your word is a lamp to my feet, and a light to my path. Psalm 119: 105
For God, who said that light shone out of darkness, is the one that has shone in our hearts, to illuminate the knowledge of the glory of God in the face of Christ. 2 Corinthians 4: 6
Note: @sirknight started a contest and its daily topics are:
Sunday-light
Monday-darkness
Tuesday - animal kingdom
Wednesday-Structures
Thursday-ForcesNature
Friday-AmorBeautyFreedom
Saturday-Agriculture