Refusal to take an oath (nakl al-yamin)—a recognized mode of proof in Islamic legal tradition—refers to a defendant’s abstention from swearing without transferring the oath to the claimant. Despite its relevance in civil litigation, this legal institution has received limited scholarly attention, particularly from a comparative perspective involving the five major Islamic schools and the statutory frameworks of Iran and Afghanistan. The necessity of this inquiry arises from the interpretive divergence concerning nakl, which significantly influences judicial outcomes; a precise doctrinal and legal analysis may thus enhance judicial coherence and inform legal reform. This study investigates the jurisprudential foundations of oath refusal across the five schools and examines the corresponding approaches in Iranian and Afghan law. The central hypothesis posits that nakl may serve as an independent ground for judicial decision-making under both Islamic jurisprudence and codified law. Employing a descriptive-analytical and comparative method, and drawing upon authoritative jurisprudential and statutory sources, the research reveals that while all schools uphold the principle of oath-taking, they differ markedly in their treatment of refusal. Some permit adjudication based on nakl, others view it as a basis for oath transfer, and yet others propose judicial suspension. These doctrinal variances are also mirrored in the relevant legal systems of Iran and Afghanistan.