In Islam, the lunar cycle is a foundational principle of divine timekeeping, established by Allah as a sign (ayah) and a practical guide for humanity. According to search-discovered classical scholarship on Quran 2:189, the new moons ('ahillah') were designated as 'measurements of time for the people and for Hajj,' thereby creating a universally accessible calendar. Tafsir on Quran 10:5, including the analysis of Ibn Kathir, deepens this understanding by presenting the moon as a 'light' (nūr) with determined phases, allowing for the precise 'calculation of years and the reckoning of time.' This lunar system, known as the Hijri calendar, is not merely a celestial phenomenon but a sacred institution that governs the timing of Islam's most vital rituals, such as the fast of Ramadan and the annual pilgrimage. The synthesis of these verses demonstrates that observing the moon is an act of both practical necessity and spiritual reflection, connecting believers to the cosmic order established by the Creator.