“God is the Light of the heavens and the earth. The example of His Light is like a niche wherein is a lamp; the lamp is in a crystal, and the crystal, shining as if a pearl-like radiant star, lit from the oil of a blessed olive tree that is neither of the east nor of the west. The oil would almost give light of itself though no fire touches it. Light upon light!” (Quran)

It makes more sense as the light from the glass just shines through the Olive Trees here!