At the opposite extreme is a weak, watery heart, lacking strength or firmness. It takes on every form but has no power to retain those forms or to influence anything else. Whatever comes into contact with it affects it, whether strong or weak, good or corrupt.
Within the glass is a lamp: the light in the wick, which bears it.
That light has a fuel: oil pressed from an olive tree in an ideally situated spot, where the sun reaches it at the beginning and end of the day. Its oil is among the purest and freest from impurities, so pure that it almost shines without fire.
This is the fuel of the lamp’s light. Likewise, the light of the lamp within the believer’s heart draws its fuel from the tree of revelation, the most blessed of all things and the furthest from deviation. Rather, it is the most balanced, just, and excellent of all ways. It has deviated neither as Christianity has deviated nor as Judaism has deviated; rather, in everything it holds the middle course between the two blameworthy extremes.
This, then, is the fuel of the lamp of faith in the believer’s heart.
Since that oil has become so pure that it almost shines by itself, when fire touches it, its radiance intensifies and the fire within it lends greater strength to its light. Thus it becomes light upon light.
So it is with the believer: his heart is luminous, almost able to recognize the truth through his innate disposition and reason, yet it has no fuel of its own. Then the fuel of revelation comes, touches his heart, and mingles with its joy. Revelation adds further light to the light upon which Allah Most High created him. The light of revelation thus joins the light of his innate disposition: light upon light. He almost speaks the truth even before hearing a transmitted report concerning it. Then he hears the report, finding it in accord with what his innate disposition has borne witness to, and it becomes light upon light.
Such is the believer’s condition: through his innate disposition he perceives the truth in general, then hears the transmitted report setting it out in detail. His faith thus arises from the testimony of revelation and the testimony of his innate disposition.