"Whoever supposes that faith is realized through speculative theology, abstract proofs, or academic devisions is an innovator. On the contrary, faith is a light that God, the Sublime and Exalted, casts into the hearts of His servants with bounty and grace from His presence. Sometimes faith is evidenced internally and is impossible to express; sometimes, through a vision while asleep; other times, by witnessing the state of a pious man and receiving the emanation of his light as a result of his companionship and presence; and then there are times when faith comes by the concurrence of circumstance. Indeed, a Bedouin came to the prophet ﷺ denying and disavowing him. But when his eyes fell upon his radiant aspect—may God increase its dignity and nobility—he saw in it the light of prophethood and exclaimed, "By God! This is not the face of a liar!" He then implored the prophet ﷺ to explain Islam to him and immediately embraced it."
— Abū Ḥāmid Al-Ghazzālī.