The sources of Islamic Jurisprudence are the Quran and hadiths, along with scholarly consensus (which is based on the first two.) To issue a ruling based on them, a scholar is needed to tell whether a question has been answered unequivocally by these sources, and to issue a verdict based on similar cases if it hasn’t. To do all this, he must have encyclopedic knowledge of the sciences of the Arabic language, the Quran, hadiths, and sayings of previous scholars along with their reasoning. Finally, he must be very exacting, fearful of making a mistake, and have radiating intelligence.
A scholar of this rank, called a mujtahid, is very rare. Moreover, because of the gravity of the task, the early generations of Muslims were extremely particular about the qualifications of such scholars. Even among the Companions of the Prophet themselves, only around ten to thirty were mujtahids.
If it was recognized among the early generations that a person was a mujtahid, he would naturally attract many students. Over time, however, students of four scholars in particular, those of Abu Hanifah, Malik, Al Shafi’i, and Ahmad ibn Hanbal became very many. This was because they were the top scholars of their times; they mastered the Quran and hadiths more than others. Their proofs and reasoning for their verdicts were impeccable.
Their top students, some of whom were mujtahids themselves, narrated their sayings and reasoning to the next generation, and answered new questions based on the methodology of the founder. They would also weed out weak verdicts of the founder, if they were convinced that he would have changed his verdict based on what they had of proofs. This process continued from generation to generation. Passing through the hands of their scholars, the four schools became highly developed and documented; they had authenticated verdicts for most issues one would encounter, and sophisticated and comprehensive reasoning in terms of the Quran and hadiths.
Eventually all students of jurisprudence would learn through these schools, because they became the most effective and reliable way of learning the teachings of the Prophet. Moreover, caution dictates that one should go by the verdicts that thousands of experts on Quran and hadiths had scrutinized and accepted over hundreds of years within these schools.
Adherence to these schools preserves the unity of Muslims by preventing too many scattered and weak opinions, or impostors from claiming to be mujtahids. They have now been evaluated and tested for more than 1100 years since their establishment. This means that the remaining differences of opinion between these schools exist for very good reasons; the right answer cannot be known with complete certainty.
Authored by Shaykh Abu Adam al Naruiji