Allah is the light of the heavens and the earth; a likeness of His light is as a niche in which is a lamp, the lamp is in a glass, (and) the glass is as it were a brightly shining star, lit from a blessed olive-tree, neither eastern nor western, the oil whereof almost gives light though fire touches it not-light upon light-Allah guides to His light whom He pleases, and Allah sets forth parables for men, and Allah is Cognizant of all things.
This is one of my favorite passages from the Qur'an as it seeks to describe the light of God. One can truly appreciate how accurate this description is when one considers closely the layers of description in the context of how life was lived during that time.
First, the light is in a niche. This implies a building (not a tent) that has an enclosed shelf that allows light to be concentrated in its brilliance and also sheltered from wind or being tipped over. So the imagery first establishes that the light of God is found in a fixed place where the light is both concentrated in intensity and certain in its stability. Then the light is described as being in that niche within a beautiful glass. Remember that glass was a extreme and expensive rarity in those times. And so the glass itself is precious, and it is described as being of the finest quality so that it shines like a star. This is not only a description of the precious beauty of the light of God, but also an analogy that the light of God is his knowledge brought from heaven and given to humans to observe here on earth, like a star that is accessible.
Then the type of oil that is used in this lamp that describes the light of God is specified as being from the olive tree. This is reference to both the beauty of olive oil (golden or light green, and even white in great purity) and also the incredible life giving importance of the olive tree and its essence, its fruit. So the light of God is compared to a light in a niche in glass like a star fueled by the "blessed" olive oil, oil that is so pure that it is both life giving and glows almost as if the oil itself was on fire, though it is not. So the light of God is compared to an oil that fuels the fire but glows without being burned and consumed itself within the holding vessel of the lamp. This image would have had great beauty and profound significance to all who lived during that time.
The beautiful star like light in the niche is thus explained as also being an analogy of how God gives wisdom in the form of parables (the contained and brilliant light in the niche being as if a "piece" of God's wisdom given to humans), and the light being given to those who God wills that they should have it (again, the glass and the niche with pure blessed oil implying its preciousness and form of a gift) and that God knows all, because this example of the light is just a fraction of the entirety of God's light.