The Quran

۞ اللَّهُ نورُ السَّماواتِ وَالأَرضِ ۚ مَثَلُ نورِهِ كَمِشكاةٍ فيها مِصباحٌ ۖ المِصباحُ في زُجاجَةٍ ۖ الزُّجاجَةُ كَأَنَّها كَوكَبٌ دُرِّيٌّ يوقَدُ مِن شَجَرَةٍ مُبارَكَةٍ زَيتونَةٍ لا شَرقِيَّةٍ وَلا غَربِيَّةٍ يَكادُ زَيتُها يُضيءُ وَلَو لَم تَمسَسهُ نارٌ ۚ نورٌ عَلىٰ نورٍ ۗ يَهدِي اللَّهُ لِنورِهِ مَن يَشاءُ ۚ وَيَضرِبُ اللَّهُ الأَمثالَ لِلنّاسِ ۗ وَاللَّهُ بِكُلِّ شَيءٍ عَليمٌ

(Saheeh International)

Allāh is the Light¹ of the heavens and the earth. The example of His light² is like a niche within which is a lamp;³ the lamp is within glass, the glass as if it were a pearly [white] star lit from [the oil of] a blessed olive tree, neither of the east nor of the west, whose oil would almost glow even if untouched by fire. Light upon light. Allāh guides to His light whom He wills. And Allāh presents examples for the people, and Allāh is Knowing of all things.

i.e., the source and bestower of light and enlightenment.
His guidance in the heart of a believing servant.
Literally, "a burning wick," which is the essence of a lamp.