The Quran repeatedly highlights the Moon's function as a clear sign (āya) of Allah’s creation and meticulous ordering of the cosmos. As mentioned in the introduction, “He made the sun a shining light and the moon a radiant light, and determined for it phases”, emphasizing its role in establishing the calculation of time for humanity. This divine arrangement directly impacts the practical aspects of Islamic worship, particularly the lunar calendar.

The Prophet Muhammad (ﷺ) provided clear guidance on using the sighting of the new crescent moon (hilāl) to determine the start and end of the months, especially for the sacred month of Ramadan. Hadith traditions explicitly state: “When you see the crescent (of the month of Ramadan), start fasting, and when you see the crescent (of the month of Shawwal), stop fasting; and if the sky is overcast (and you can't see it) then regard the month of Ramadan as of 30 days” Bukhari 30:10. This instruction is reiterated in numerous narrations, such as “Do not fast unless you see the crescent (of Ramadan), and do not give up fasting till you see the crescent (of Shawwal), but if the sky is overcast (if you cannot see it), then act on estimation (i.e. count Sha'ban as 30 days)” Bukhari 30:16, and “The month (can be) 29 nights (i.e. days), and do not fast till you see the moon, and if the sky is overcast, then complete Sha'ban as thirty days” Bukhari 30:17. These narrations underscore the importance of direct lunar observation in determining religious timings, linking the physical observation of the Moon directly to acts of worship.

The legal schools (madhabs) operationalize this prophetic guidance. The rulings imply a consensus among the early Muslims and subsequent jurists that the lunar month begins and ends with the confirmed sighting of the new crescent moon. In cases of an overcast sky, the default is to complete the preceding month as thirty days, ensuring continuity and order in religious observances. This practice, established by the Prophet (ﷺ), demonstrates how the Moon's visible cycle is integrated into the very fabric of Islamic religious life, fulfilling its role as a divine marker for human activity.

Among the most extraordinary events associated with the Moon in Islamic tradition is its miraculous splitting. The Quran explicitly refers to this phenomenon: “The Hour has approached and the moon has split”. This verse is a direct reference to a miracle granted to Prophet Muhammad (ﷺ) in Mecca, witnessed by disbelievers as a sign of his prophethood.

Numerous Hadith corroborate this event, providing further details. Anas narrates “That the Meccan people requested Allah's Messenger (ﷺ) to show them a miracle, and so he showed them the splitting of the moon” Bukhari 61:141. `Abdullah bin Masud adds that “During the lifetime of the Prophet (ﷺ) the moon was split into two parts and on that the Prophet (ﷺ) said, "Bear witness (to this)” Bukhari 61:140. Other reports specify that one part of the moon went towards a mountain, and the other beyond it, or that they saw the Hira' mountain between the two halves (Bukhari 63:93, 65:385, 65:386; Muslim 52:28, 52:29).

This miracle served as a powerful, undeniable sign for the disbelievers, yet many still rejected it. Ibn Kathir explains that despite the clear evidence, the Meccans accused the Prophet of sorcery, illustrating their hardened hearts. The verse “The Hour has approached and the moon has split” also links this miracle to the broader theme of the approaching Day of Judgment, signifying that even the most fundamental celestial bodies can be altered by Allah's command, thus foreshadowing the cataclysms of the End Times. The splitting of the Moon is remembered as a powerful testament to the truth of Prophet Muhammad's (ﷺ) message and Allah's omnipotence.

The Moon appears as a significant motif in descriptions of the Day of Resurrection and the afterlife, particularly in relation to humanity's vision of Allah and the splendor of Paradise.

Several Hadith traditions convey that believers will see Allah on the Day of Resurrection as clearly as they see the full moon on a clear night. When asked, “O Allah's Messenger (ﷺ)! Shall we see our Lord on the Day of Resurrection?”, the Prophet (ﷺ) responded, “Do you have any difficulty in seeing the moon on a full moon night? They said, "No, O Allah's Messenger (ﷺ)."” He then confirmed, “So you will see Him, like that” (Bukhari 0:0, 10:201, 65:103, 97:64, 97:65; Muslim 1:356, 1:359). This analogy underscores the clarity and unimpeded nature of the vision of Allah for the believers, likening it to the easiest and most beautiful of visible phenomena. Jarir bin `Abdullah's narration further emphasizes this, stating, “You will see your Lord as you see this moon, and you will have no trouble in looking at Him” (Bukhari 65:372, 9:31, 9:49, 97:61, 97:63; Muslim 55:22). This profound spiritual promise, facilitated by the vivid imagery of the full moon, highlights the ultimate reward for the faithful.

Moreover, the brightness of the Moon is used to describe the radiant beauty of the inhabitants of Paradise. The Prophet (ﷺ) stated, “The first group (of people) who will enter Paradise will be (glittering) like the moon when it is full” (Bukhari 59:56; Muslim 53:16, 53:19, 53:20). Other narrations expand on this, describing their hearts as one, free from enmity, and their bodies emitting the scent of musk (Bukhari 59:57, 59:64). The image of faces shining like the full moon is also applied to the seventy thousand (or seven hundred thousand) of the Prophet's followers who will enter Paradise without reckoning (Bukhari 59:58, 77:29, 81:131, 81:132, 81:143; Muslim 1:428, 1:429). This imagery conveys the immense honor, purity, and bliss awaiting the righteous in the Hereafter.

On the contrary, the Moon is also mentioned in the context of the Day of Resurrection when its light will be extinguished. The Prophet (ﷺ) said, “The sun and the moon will be folded up (deprived of their light) on the Day of Resurrection” Bukhari 59:11. This stark contrast between its radiant beauty and its ultimate cessation of light serves as a powerful reminder of the temporary nature of this world and the eternal reality of the next.

Islamic teachings regarding lunar and solar eclipses highlight the Moon's role as a sign of Allah's power, rejecting pre-Islamic superstitions and instituting a specific form of worship. The Hadith clearly state: “The sun and the moon do not eclipse because of someone's death or life but they are two signs amongst the signs of Allah, so pray whenever you see them” (Bukhari 16:16, 16:19, 16:22, 59:12, 59:13, 59:15, 77:3; Muslim 10:2, 10:23, 10:24, 10:30, 10:31).

These narrations arose in response to an event where the sun eclipsed on the day the Prophet's son, Ibrahim, died. People began to attribute the eclipse to his death, a common pagan belief that celestial phenomena were linked to human events. The Prophet (ﷺ) immediately corrected this misunderstanding, clarifying that eclipses are divine signs, not omens for human births or deaths. Instead of succumbing to superstition, Muslims are commanded to engage in prayer (Salat al-Kusuf), supplication, and remembrance of Allah until the eclipse passes. This practice redirects human attention from superstitious fear to humble submission and worship of the Creator, reinforcing the idea that the Moon, like the Sun, is entirely subservient to Allah's will.

Beyond fasting, the Moon's phases are also crucial for other religious observances, particularly the annual pilgrimage of Hajj. The Hadith show that during Hajj, some concessions were made based on the moon's position. For example, during the Night of Jam' (Muzdalifa), weaker individuals, particularly women, were permitted to leave early (before dawn) after the moon had set, to proceed to Mina for the ritual of stoning the Jamra. Asma' and Abdullah bin `Umar both reported that the Prophet (ﷺ) granted this permission, acknowledging the practical needs of the weak and elderly (Bukhari 25:156, 25:159; Muslim 15:326). This demonstrates the Prophet’s (ﷺ) pragmatic approach and concern for the ease of his followers within the framework of divine timing and lunar observation.

Furthermore, Aisha (Allah be pleased with her) reported that they set out for the Farewell Pilgrimage “near the time of the appearance of the new moon of Dhul-Hijja” Muslim 15:123. This highlights that even the commencement of the Hajj season, and the different forms of Ihram (sacred state) that pilgrims would undertake, were timed with the lunar calendar, emphasizing the pervasive influence of the Moon's cycles on major Islamic rituals.

Beyond its functional and miraculous aspects, the Moon also serves as a powerful aesthetic and metaphorical device in Islamic tradition, particularly in descriptions of spiritual beauty and tranquility.

The Prophet Muhammad's (ﷺ) own countenance is often described with the imagery of the Moon, signifying his radiant and beautiful character. Al-Bara' noted that the Prophet's face was not as sharp as a sword but “as bright as a moon” Bukhari 61:61. Ka`b bin Malik described the Prophet's face glittering with happiness, “as if it was a piece of the moon” Bukhari 61:65. Jabir b. Samura further clarified that his face was “round and like the sun and the moon” Muslim 43:142, combining the brilliance of both celestial bodies. This metaphorical usage elevates the Moon beyond a mere object of observation to a symbol of spiritual radiance, purity, and joy, reflecting the Prophet's esteemed status.

Similarly, in Abu Dharr's narration, when the Prophet (ﷺ) was walking alone at night, Abu Dharr chose to walk “in the shade, away from the moonlight”, respecting the Prophet's privacy, which subtly implies the brightness of the moonlit night (Bukhari 81:32; Muslim 12:42). This detail adds a touch of everyday reality, showing the Moon's practical role in illuminating the night and shaping human experience, even in a narrative with deep spiritual lessons.

In conclusion, the Moon in Islamic tradition is a profoundly significant entity, intricately woven into the theological, devotional, and practical life of Muslims. From its role as a radiant light for timekeeping and a catalyst for religious rituals like fasting and Hajj, to its manifestation as a miraculous sign of prophethood, and its metaphorical use in describing divine vision and heavenly beauty, the Moon serves as a constant reminder of Allah's grandeur, the truth of His revelation, and the ultimate destiny of humanity. It demands contemplation, provides guidance, and illuminates both the physical and spiritual paths for believers.