The most fundamental understanding of nur in Islam is its attribution to Allah Himself. The Quran declares Allah as the Light of the heavens and the earth, a verse that positions Him as the illuminator and sustainer of all existence. This divine light is not a physical emanation but a metaphysical attribute, signifying His omniscience, omnipresence, and ultimate source of guidance. This profound truth is echoed in the Prophet Muhammad's supplications, where he frequently invoked Allah, saying, "O Allah! All the Praises are for You; You are the Light of the Heavens and the Earth" (Bukhari 97:124, 97:15, 97:68; Muslim 6:236). This prayer reaffirms the believer's recognition of Allah as the primal, uncreated light that illuminates all things.

Yet, this divine light remains beyond human sensory perception in this life. When Abu Dharr asked the Messenger of Allah (ﷺ), "Did you see thy Lord?", the Prophet replied, "(He is) Light; how could I see Him?" Muslim 1:348. This indicates that Allah's light is not observable by human eyes in its true form, underscoring His transcendence. Furthermore, the Prophet described Allah's majesty by stating, "His veil is the light," and in another narration, "His veil is the fire. If he withdraws it (the veil), the splendour of His countenance would consume His creation so far as His sight reaches" (Muslim 1:350, 1:351). This imagery portrays the immense power and intensity of Allah's light, which is veiled from creation as an act of mercy, for its full manifestation would be overwhelming. The very first creations are tied to this divine light, as the angels themselves were "born out of light," while Jinns from fire and Adam from clay Muslim 55:78, further cementing light's association with purity and closeness to the divine.

The divine light of Allah extends to His revelations and messengers, serving as the means by which humanity finds guidance. The Quran itself is repeatedly characterized as a source of light, a testament to its role in dispelling the darkness of ignorance and misguidance. Through His divine message, Allah promises to [bring them out of darkness into light](5:15-16, 2:257). This transition from "darkness" (referring to polytheism, error, and ignorance) to "light" (monotheism, truth, and knowledge) is the core purpose of divine revelation. The Quran is therefore described as containing "right guidance, the light," for "whoever adheres to it and holds it fast, he is upon right guidance and whosoever deviates from it goes astray" Muslim 44:57.

Prophet Muhammad (ﷺ) is the direct conduit of this divine light to mankind. The Quran refers to him as a burning lamp, illuminating the path for humankind. The companions recognized this, with Ibn Rawaha stating in verse, "We have Allah's Messenger (ﷺ) with us who recites the Holy Qur'an in the early morning time. He gave us guidance and light while we were blind and astray, so our hearts are sure that whatever he says, will certainly happen" Bukhari 78:177. Even after the Prophet's passing, `Umar reminded the community that "if Muhammad is dead, Allah nevertheless has kept the light amongst you from which you can receive the same guidance as Allah guided Muhammad with that" Bukhari 93:79, referring to the enduring light of the Quran and Sunnah. Gabriel's joyous announcement to the Prophet of "two lights given to you which have not been given to any prophet before you: Fatihat al-Kitab and the concluding verses of Surah al-Baqara" Muslim 6:305 further emphasizes the unique and illuminating power of these revealed texts for the Muslim community.

The concept of nur extends to the actions and states of believers, who strive to embody this divine guidance. Through their devotion, they acquire an inner light that guides them in this life and the next. Cleanliness, especially through ablution (wudu'), is a tangible practice that manifests this spiritual light. The Prophet (ﷺ) foretold that on the Day of Resurrection, his people "would come with bright faces and bright hands and feet on account of the marks of ablution" Muslim 2:47, indicating that physical purity for worship leads to spiritual radiance.

Beyond ritual purity, core acts of worship are themselves described as light. The Prophet (ﷺ) declared that "prayer is a light, and charity is proof (of one's faith) and endurance is a brightness" Muslim 2:1. These acts illuminate the believer's path, providing clarity and strength in the face of life's challenges. The spiritual light can even manifest supernaturally, as seen when two companions of the Prophet (ﷺ) walked out on a very dark night and "two things that resembled two lamps lighting the way in front of them" appeared, separating to accompany each man home (Bukhari 61:143, 63:30, 8:113). Such miracles underscore the tangible presence of divine support and illumination for those devoted to Allah.

The understanding of nur also extends to practical guidance concerning physical light and its proper use within Islamic ethics. The Prophet Muhammad (ﷺ) provided instructions that safeguard life and property, such as advising believers to "put out the lights" (Bukhari 79:67, 79:68) before sleeping. This directive, given at a time when oil lamps posed fire hazards, reflects a proactive approach to safety, ensuring that "the evil creature (the rat) should not pull away the wick and thus burn the people of the house."

Furthermore, the sources clarify the ethical boundaries regarding the use of materials for illumination. The Prophet (ﷺ) explicitly forbade the use of certain impure substances, such as the fat of dead animals, for lighting. When asked about using it for greasing boats, hides, and "for lights," he categorically stated, "No, it is illegal" (Bukhari 34:182; Muslim 22:87). This ruling emphasizes adherence to purity and avoiding benefit from forbidden substances, even for practical purposes like light. The proper observation of prayer and fasting times also relies on the discerning eye for natural light, with the onset of the true dawn (when streaks of light are spread horizontally) marking the beginning of the fast, distinguishing it from the false dawn Muslim 13:50. Similarly, breaking the fast is determined by the disappearance of the sun's light and the appearance of night from the west (Muslim 13:65, 13:66).

The concept of nur culminates in the Hereafter, where light serves as a clear differentiator between the righteous and the damned, and a sign of divine favor. The Quran promises believers that their inner light of faith will manifest on the Day of Judgment, as their light will run before them and on their right hands, ensuring their safe passage to Paradise. This imagery starkly contrasts with the fate of those who rejected divine guidance.

On that momentous Day, the physical lights of this world will diminish. The Prophet (ﷺ) informed that "The sun and the moon will be folded up (deprived of their light) on the Day of Resurrection" Bukhari 59:11, signaling the end of the temporal order and the beginning of eternal realities. Signs preceding the Hour also involve light, such as a fire emerging from the land of Hijaz "and it will throw light on the necks of the camels at Busra" Bukhari 92:65. For the believer, however, the ultimate manifestation of personal light will be their intimate conversation with Allah. On the Day of Resurrection, a believer "will be brought to his Lord, the Exalted and Glorious, and He would place upon him His veil (of Light) and make him confess his faults," ultimately leading to forgiveness and the bestowal of their book of good deeds Muslim 50:61. This intimate veiled encounter highlights light as a symbol of divine mercy, protection, and honor for the faithful.

In conclusion, nur is a central and dynamic concept in Islam, extending from the divine essence of Allah to the guidance provided by His revelations and prophets, and manifesting in the spiritual and practical lives of believers, ultimately illuminating their path to the Hereafter. It is a unifying theme that underscores the pervasive presence of truth, wisdom, and divine benevolence throughout existence and beyond.