TOPAsceticism is a life-style, a process, and though in both Christianity and Islam the way of life it characterized was understood to have its own merits and its own rewards, eventually in both traditions it came to be regarded as the preparatory means to an even higher, and far rarer, state, the experience of the divine: the devout Sufi might also aspire to be a mystic.
The scriptural accounts of Moses on Sinai and Jesus on Tabor served, when and where needed, as Jewish and Christian paradigms of the vision of God. The Muslim had no such straightforward narrative text in the Quran to certify Muhammad for the same purpose, and so the mystics of Islam turned instead for their inspiration to the famous "Light Verse."
God is the Light of the heavens and the earth.
The semblance of His Light is that of the niche in which is a lamp, the flame within the glass, the glass as it were a glittering star, lit with the oil of a blessed tree, the olive, neither of the East nor of the West, whose oil appears to light up even though fire touches it not— light upon light.
God guides to His Light whom He will. So does God advance precepts [or "allegories"] for men, For God has knowledge of every thing. (Quran 24:35)
The last sentence in the verse reads like an open invitation to allegorical exegesis, and so it was generally interpreted, here from the work entitled The Pure in the Interpretation of the Quran by the Shi’ite scholar al-Kashi (d. 1505 C.E.). His interpretation, which is overtly Shi’ite in intent, goes back, as he tells us, to another, much earlier eminence in that tradition, Ibn Babuya al-Qummi (d. 939 C.E.). And Qummi's authorities are no less than the fifth and sixth Shi’ite Imams, Muhammad al-Baqir (d. 731 C.E.) and Jafar al-Sadiq (d. 756C.E.).
In The Oneness (of al-Qummi) it is reported, on the authority of al-Sadiq: What is at question here is a simile that God has fashioned for us.
God is the Light of the Heavens and the Earth: Just so, said al-Sadiq.
His Light: al-Sadiq said: This refers to Muhammad.
That of a niche: al-Sadiq said that what is meant here is Muhammad's breast.
In which is a lamp: al-Sadiq said: In which is the light of knowledge, that is, of prophecy.
The flame within the glass: al-Sadiq said: The knowledge of the Messenger of God went forth from the latter into the heart of Ali.
… neither of the East nor the West: According to al-Sadiq these words refer to the Commander of the Believers, Ali ibn Abi Talib, who was neither a Jew nor a Christian.
Whose oil appears to light up even though fire touches it not: al-Sadiq said: The knowledge would issue forth from the mouth of the knowing one of the family of Muhammad [that is, Ali] even if Muhammad had not spoken it.
Light upon light: al-Sadiq said that this means from one Imam to the next.
Then Kashi turns to another Shi̔ite commentator, al-Tabarsi (d. 1153 C.E.) for a somewhat more general interpretation of the same verse.
It is said … (by Tabarsi) from the Imam al-Baqir in a Tradition that the verse "God is the Light of the heavens and the earth" means: "I [that is, God] am the rightly guided director of the heavens and the earth. The knowledge that I have given, namely, My light through which the guidance results, ‘is like a niche wherein is a lamp.’ The niche is the heart of Muhammad, and the lamp is his light, wherein lies knowledge." Further, God's words "the flame in a glass" mean: "I [that is, God] want to lay hold of you and what is with you so that I might manifest the Executor [a standard Shi̔ite designation for Ali] like the flame in the glass, ‘as it were a glittering star.’ Then will I give men news of the excellence of the Executor."
Lit with the oil of a blessed tree: The root of that blessed tree is Abraham. This is referred to in God's words: "The mercy of God and His blessings be upon you, O people of the House. Surely he [that is, Abraham] is worthy of praise and glory" (Quran 11:76). …
That is neither of the East nor the West means: You are neither Jews, so that you would perform the prayer facing toward the west [that is, Jerusalem] nor Christians, so that you would face toward the east. Rather you follow the creed of Abraham, of whom God has said: "No, in truth Abraham was neither a Jew nor a Christian, but a hanif who had submitted to God. Certainly he was never one of the idolaters" (Quran 3:60). (Kashi ad. loc.)