Ijma (Arabic: ‘consensus’ or ‘agreement’) is the third source of Islamic law after the Quran and Sunnah, and in some formulations ranks above analogical reasoning (qiyas) as a source of binding authority. The classical definition: the consensus of qualified Muslim scholars (mujtahids) on a legal question constitutes a binding ruling — based on the hadith ‘My community will not agree on an error.’ Ijma provides stability and normative force to rulings that might otherwise remain disputed. The debate about the scope of ijma: whose consensus counts? Only the companions of the Prophet? The scholars of a particular city (Medina for the Malikis)? All scholars of a generation? All qualified scholars alive at any time? The practical difficulty: achieving actual documented consensus across the entire scholarly community is nearly impossible. Nevertheless, ijma operates implicitly in Islamic law to ratify rulings that have become universally accepted over centuries — such as the canonical status of the four madhabs themselves.