Allah has established Islamic rules to ensure the welfare of humanity. Even if the stream of divine messages through the Holy Prophet Muhammad (peace and blessings be upon him) were to cease, the framework for addressing the myriad challenges faced by every human being until the Day of Resurrection remains intact within this system. Nonetheless, it is essential for mujtahids and researchers of Islamic law to derive new provisions that align with contemporary lifestyles, drawing from various primary and supplementary sources of Shariah. One such supplementary source is Istishab, which plays a significant role in this process. This article aims to explore the concept of Istishab, presenting the perspectives of different schools of thought regarding its application. It also examines the reasons for the disagreements surrounding it, assesses its validity in the context of comparative fiqh, and evaluates its applicability across various modern fields. Through a descriptive and analytical approach, this article demonstrates that while the schools of fiqh hold diverse views on Istishab, they collectively recognize it as a legitimate source of Islamic law. Its necessity and significance in formulating Shari’ah rules for new issues have been acknowledged at various levels of Islamic jurisprudence