Whenever you sight the new moon (of the month of Ramadan) observe fast. and when you sight it (the new moon of Shawwal) break it, and if the sky is cloudy for you, then observe fast for thirty days.
The Book of Fasting - Sahih Muslim 1081a
This hadith establishes the fundamental principle for determining the beginning and end of Ramadan through lunar sighting, providing guidance for cases of obscured visibility.
Primary Ruling of Moon Sighting
The command "observe fast" upon sighting the Ramadan crescent establishes that fasting becomes obligatory upon verified visual confirmation, making physical sighting the primary legal means for determining the month's commencement.
Similarly, the instruction to "break it" upon sighting the Shawwal crescent indicates the obligation to cease fasting and celebrate Eid, demonstrating the complementary nature of both sightings in regulating the complete fasting period.
Scholarly Interpretation of Cloudy Conditions
Classical scholars interpret "if the sky is cloudy" as encompassing any atmospheric condition that prevents clear moon sighting, including dust storms, fog, or heavy cloud cover that obscures visibility.
The directive to "observe fast for thirty days" in such cases represents a precautionary principle (iḥtiyāṭ) ensuring the complete fulfillment of Ramadan's obligation while avoiding potential shortchanging of the sacred month.
Legal Methodology and Contemporary Application
Traditional jurists derived from this hadith that when the moon is obscured, Muslims should complete thirty days of Sha'ban before commencing Ramadan, and similarly complete thirty days of Ramadan before celebrating Eid.
Scholars emphasize that this completion method preserves the lunar nature of Islamic worship while providing certainty in religious practice, though contemporary discussions address the permissibility of astronomical calculations as supplementary means.
Spiritual Dimensions
This prophetic teaching cultivates communal awareness and unity as Muslims collectively await the crescent, transforming a astronomical event into an act of worship that strengthens communal bonds and religious consciousness.
The reliance on physical sighting rather than calculations serves as a reminder of Islam's practical nature and the importance of tangible religious observances that engage the entire community in worship.