Introduction
The fast is a religious obligation for every Muslim and constitutes the fourth pillar of Islam. It can be observed individually or take the form of a collective rite on certain occasions. The most important is that of the month of Ramadan, the ninth month of the Islamic calendar, during which believers are required to fast every day until nightfall. During this month, the gates of paradise are open and the devil is chained.1. In this article, we will present the history of fasting in Islam and the various theories related to it.Fasting: a universal practice
Fasting is a practice observed, either individually or as a collective rite, across many cultures. In the Torah, Moses fasts for forty days after receiving the Ten Commandments (Exodus 34:27-28). Jews fast during Yom Kippur, the "Day of Atonement," and observe dietary restrictions at certain times of the year. The Lenten fast among Christians lasts for forty days—hence its name Quadragesima—in memory of Jesus' forty days in the desert. The practice is also well attested outside the Judeo-Christian sphere. Among Aboriginal Australians, in New Guinea, and among the Indians of the Andaman Islands, fasting is a part of passage rites, preparing access to hidden knowledge2. In the mystery cults of ancient Greece, candidates for initiation had to fast for a set period and abstain from certain foods3. A strict fast is imposed in certain religions for priestly ordination. In Christianity, this practice is documented from the time of the early Apostles (Acts 13:1-4), and in the Western Church, priests were required to fast for four days before ordination. A similar custom can be found among Eskimo priests and healers, Zulu (Southern Africa), and Sami (Norway)4. On another note, fasting is said to be used to make a curse more effective against a designated enemy, based on beliefs found in the Banks Islands and even in Morocco until the last century5. Finally, some traditions observed among the Maori and Native Americans state that warriors must observe a fasting period before going into battle6.
Regarding pre-Islamic Arabia, data are scarcer and less conclusive, although there is no reason to assume a priori that Arabs were unaware of a phenomenon that occurs across all regions and eras. On the one hand, Arab populations had largely converted to Judaism and Christianity, and followed their religious precepts—including fasting. An example is found in an inscription in northern Arabia, where a certain "Shullay, son of Ashwû" refers to the Festival of Unleavened Bread, during which Jews abstain from consuming leavened bread7. On the other hand, Muslim sources indicate that polytheistic Arabs fasted during the month of Rajab, one of the sacred months of the pre-Islamic era. The tradition of fasting during Rajab persisted in emerging Islam, despite strong opposition from some purists8.
Why do we fast?
One might question the reasons that drive humans to voluntarily deprive themselves of food. At first glance, it may seem irrational to engage in a practice that is often uncomfortable or exhausting. Religious explanations cannot fully answer this question—they are actually the consequence, not the cause, of the phenomenon. Many theories have been proposed by specialists to explain the emergence of fasting throughout human history.
First, we will mention the "Big Gods" theory formulated by several researchers in evolutionary psychology. According to this theory, successful organized societies owe their strength to shared belief in one or more moralizing deities, such as the God of major monotheistic religions. This belief would strengthen cooperation and trust among community members. In this context, rites such as fasting, dietary taboos, and sometimes self-mutilation serve as tests of loyalty and adherence to the group as a whole9. It has been demonstrated that groups with strict norms have a higher survival rate than more liberal groups. In other words, fasting is a "costly signal" that demonstrates "a hard-to-fake commitment to the beliefs of the religious group" ("a hard-to-fake commitment to the beliefs of the religious group")10. Several studies in clinical psychology have confirmed this hypothesis. One such study, involving about ten male subjects who did not know each other before the experiment, showed that participants enhanced their cooperation and solidarity after their fasting period11.
Fasting could also be viewed through the lens of the handicap theory, which posits that some animal species develop traits that seem disadvantageous but actually serve as reliable markers of genetic quality. The most famous example in the animal kingdom is perhaps the peacock's tail, which males display proudly to attract females. Although its tail is a handicap, being bulky and energy-consuming, it provides a significant reproductive advantage. By sporting such extravagant plumage, the peacock signals its genetic quality and robustness: only a healthy individual capable of overcoming this physiological disadvantage can afford such an ornament. Human fasting might be an equivalent to the peacock's tail, sending a signal of health and physical vigor—and thereby improving one's position in sexual competition12.
In a different context, fasting is linked to a natural mechanism. When humans fall ill, their appetite instinctively diminishes, often leading them to abstain from eating until they recover. Thus, fasting has been associated since ancient times with the healing process. From this, it has been inferred that fasting can purify the soul13. Interestingly, today there is a form of secularization of this concept. Fasting is often presented, with arguments bordering on pseudoscience, as a means to "purify" the body.
Regarding the supposed benefits of fasting, scientific literature is much more measured about it than popular books that attribute all virtues to it14. Some benefits are undeniable, such as the regulation of blood sugar levels. Fasting also induces cellular stress that triggers autophagy, during which cells renew themselves by degrading damaged components. This process is believed to combat aging and the development of neurodegenerative and cancerous diseases. However, autophagy mainly activates after 24 hours of fasting15. The Ramadan fast, like Lent, is intermittent, with abstention from food for about 16 hours per day on average. Some studies suggest that intermittent fasting is sufficient to activate autophagy16, but it has been shown that in some cases, it can lead to cell death17. Recently, a study involving over 20,000 adults followed over a median period of eight years showed that intermittent fasting increased the risk of death from cardiovascular disease by 91%18. These results corroborate a 2022 study that found individuals observing Ramadan fasting had a higher risk of developing a heart attack in the following months19. Another study demonstrated that newborns whose mothers observed Ramadan fasting during pregnancy had an increased risk of mortality20.
Ashura: the forgotten fast of Islam
Islamic tradition unanimously reports that before Ramadan fasting, the Prophet instituted the fast of Ashura21, which took place on the 10th of the month of Muharram (the first month of the Islamic calendar). Muslim sources have preserved many accounts—often contradictory—regarding the origins of the Ashura fast and its adoption by Muhammad. One group of reports states that Arabs used to fast on this day before Islam22, although this cannot be confirmed with current knowledge.
According to other accounts, the Prophet only discovered the tradition of fasting on Ashura after migrating to Medina, having encountered Jews, and learned its significance from them. One report states that this day was celebrated by the Jews of Khaybar oasis, whose women dressed in their finest clothes for the occasion23. It is well established that the Ashura fast is an imitation of the fast observed by Jews during Yom Kippur, which occurs on the 10th of Tishri (also the first month of the Hebrew calendar)24. A hadith recorded by al-Bukhari states:
"When the Messenger of Allah arrived in Medina, he found the Jews fasting on the day of Ashura. The Prophet asked them about it, and they replied: 'It is the day on which Moses and his people were victorious over Pharaoh.' The Prophet said [to Muslims]: 'We are closer to Moses than they are, so fast on this day.'"25Here, we see that Muhammad would have adopted the Jewish practice of Medina after learning that it commemorated Moses' victory over Pharaoh. The explanation given by the Jews, however, is questionable. Jewish sources typically associate Yom Kippur with the descent of the Tablets of the Law, not with any victory of Moses26. Furthermore, it is impossible from a historical standpoint since "the biblical chronology does not allow linking Yom Kippur to any episode of the Exodus"27. According to Georges Vajda, the hadith depicting the discussion between Muhammad and Medina’s Jews would be a “Muslim invention” aimed at annexing Yom Kippur by "dejudaising" it28. It is also reported that this day was accompanied by a ceremony including dances, decorations, and celebrations around the Ka’ba, reminiscent of "certain archaic Jewish festivities, particularly those associated with the inauguration of the Jerusalem Temple"[span class="s1">29.
The Jewish origins of the Ashura fast caused controversy among Muslims, who sought to distinguish themselves from Jews. They did not hesitate to create traditions claiming that the Prophet tried to de-Judaize Ashura. One such tradition states that he attempted to move the fast to the 9th of Muharram instead of the 10th to differentiate from Jews: "When the Prophet began fasting, they told him: 'O Prophet, this is a day celebrated by Jews and Christians!' He replied: 'Next year, Inshallah (God willing), we will fast on the ninth day (to distinguish ourselves from the Jews).'" The following year, the Prophet had already passed away30. Scholar Ahmad ibn Hanbal (d. 855) reports an even more explicit tradition: "Fast on Ashura, but, to distinguish yourself from the Jews, fast one day before (the 9th) and one day after (the 11th)"31. Ashura fasting was subsequently abrogated and made non-obligatory after the adoption of Ramadan fasting, which is prescribed by the Quran itself. ‘Aisha is reported to have said that "the Messenger of Allah commanded to fast on Ashura, but when the fasting of Ramadan was prescribed, fasting on this day became optional" 32.
Fasting in the Quran
The Quran orders believers to observe fasting in cases of hindrance to pilgrimage (2:196), murder (4:92), perjury (5:89), annulment of the wife’s repudiation (58:4), or violation of hunting prohibition during sacred months (5:95). Note that in these different cases, fasting is considered only as a compensatory measure following a transgression of a prohibition. As Mondher Sfar notes, "fasting is equated with a 'punishment,' which could also be seen as the tribute owed to the divine suzerainté as a sign of recognition and servitude" 33.
The collective rite of fasting is that of Ramadan, with instructions given in a long passage (2:183-187). Verse 183 establishes the obligation of fasting, justified by the tradition of the ancestors: "O you who have believed! Fasting is prescribed for you as it was prescribed for those before you." Verse 184 provides an exception for the sick and travelers, who can make up missed days at another time of the year or redeem them through charity. The verse also allows individuals to forgo fasting by feeding a poor person. However, this creates inequality among believers, favoring those with the means to avoid fasting obligations by feeding the poor. Muslim traditionalists resolved the paradox by stating that the option in verse 184 was abrogated by the following verse. Thus, it is said that Ibn ‘Umar stated: "They (Muslims) had the choice: to fast or to feed a poor every day… and he added: this verse has been abrogated" 34. However, another tradition attributed to Ibn ‘Abbas states that "this verse is not abrogated, but concerns elderly men and women who cannot fast" 35. We see that the traditionists fabricated hadiths to explain, somewhat contradictorily, a Quranic passage that evidently caused some embarrassment. Verse 184 also indicates that fasting must be observed "on the counted days." The mention of "the counted days" puzzled Muslim exegetes. Some interpret this as referring to Ramadan itself, while others suggest it might have been a pre-Ramadan fast later abrogated with the institution of Ramadan36. Without further information, it's hard to resolve the question. Nonetheless, as Kees Wagtendonk observes, the reference to "the counted days" suggests a short period rather than a thirty-day fast. It could relate to an ancient pagan tradition associated with pilgrimage or sacrifice during the month of Rajab37. It is possible that a primitive version of the Quranic passage included a reference to such traditions in connection with the "counted days"38.
Verse 185 states that "the month of Ramadan is the one in which the Quran was revealed as guidance for people and clear proofs of guidance and salvation [...]". The association of fasting with the descent of the Book clearly has a Jewish background. In rabbinic writings, Yom Kippur fasting is linked to the descent of the Tablets of the Law to Moses. The author of verse 185 clearly draws on rabbinic traditions about the origin of Jewish fasting, replacing the descent of the Tablets with the descent of the Quran. Verse 185 is usually linked to two other passages, which in traditional interpretation also refer to the descent of the Quran:
"By the Book, full of clarity! We have sent it down during a blessed night" (44:2-3).
"Indeed, We sent it down during the Night of Decree" (97:1).
A cross-reading of these three passages (2:185; 44:2-3; 97:1) suggests that the Quran was revealed during Ramadan, during a "blessed night" known as the "Night of Decree" (Laylat al-Qadr). However, this interpretation raises several issues. It contradicts the traditional scenario where the Quran was revealed gradually over Muhammad's prophetic career, not in a single night. Furthermore, Christoph Luxenberg and Guillaume Dye have convincingly shown that verse 97:1 does not refer to the revelation of the Quran but to the descent of Jesus—and thus to the night of his birth39. Additionally, there is no consensus among Muslim scholars about the exact date of Laylat al-Qadr. Hadiths place it at various times during Ramadan, and some traditions even say the Prophet forgot its exact date40. Wagtendonk argues that the connection between Ramadan and Laylat al-Qadr is "artificial"42.
Verse 186 marks a thematic shift within this passage: "And when My servants ask you concerning Me... [say], 'I am near: I respond to the invocation of the supplicant when he calls upon Me.' Let them respond to My call and believe in Me, so that they may be rightly guided." Here, the focus is no longer on fasting but on Allah’s response to believers' requests. This verse became the foundation for establishing supplication prayers (Dua) in Islam, which are undoubtedly rooted in Arab pagan traditions43. Regardless, the verse seems out of place within the passage and is likely a later addition44.
Finally, verse 187 makes concessions to believers, allowing married Muslims to have sexual relations with their spouses during Ramadan nights. An interesting point is that the verse explicitly states that Allah permitted relations after transgressions of the rule: "Allah knows that you used to secretly converse with your wives. He has forgiven you and granted you absolution [...]." This passage only makes sense if there was previously a prohibition that Allah now intends to revoke. However, the current text of the Quran does not contain such a prohibition. Again, it raises the possibility that an earlier version of the Quran, subsequently revised, contained such a rule. This is plausible, considering that Jews and Christians abstained from sexual relations during their respective fasts, placing the Quran in line with regional customs.
Historians have extensively studied the origins of Ramadan. We have already seen that collective fasting predates Islam. Christian Lent, with its forty days of fasting, closely resembles Ramadan, although their durations are not identical. However, the Lent tradition was not always as we know it today. In the early centuries, fasting practices varied across churches and regions45. Some authors note that by the 5th century, in Egypt and Palestine, fasting lasted about six weeks, excluding Saturdays and Sundays—roughly thirty days in total. Peter Gerlitz hypothesizes that Ramadan may have originated from the Christian Lent among Arabs46. It is important to note that these thirty days were not consecutive, unlike Ramadan, and there is no evidence that this practice persisted two centuries later. Another, more convincing hypothesis suggests that Ramadan's fasting could be borrowed from Manichaeism. Influence of Manichaeism among Arabs grew from the 6th century, and Moshe Gil demonstrated in a seminal study that Manichaean ideas penetrated the communities that produced the Quran47. It is known that Manichaeans observed several fasting periods during the year, one lasting thirty days, which closely matches Ramadan’s fasting48. However, without dismissing the possibility of external influences, which are inevitable in the development of any religion, we will not adopt the hypotheses that see Ramadan merely as a "reprise" of an earlier tradition. It is clear that fasting was a widespread universal practice, without clear lineages connecting the different communities that adopted it.
