Following a mujtahid (Jurist)
Useful information: It is necessary for a Muslim to believe in the fundamentals of faith with his own insight and understanding, and he cannot follow anyone in this respect i.e. he cannot accept the word of another who knows, simply because he has said it. However, one who has faith in the true tenets of Islam, and manifests it by his deeds, is a Muslim and Mo'min, even if he is not very profound, and the laws related to a Muslim will hold good for him. In matters of religious laws, apart from the ones clearly defined, or ones which are indisputable, a person must:
either be a Mujtahid (jurist) himself, capable of inferring and deducing from the religious sources and evidence;
or if he is not a Mujtahid himself, he should follow one, i.e. he should act accordi ng to the verdicts (Fatwa) of the Mujtahid;
or if he is neither a Mujtahid nor a follower (Muqallid), he should act on such precaution which should assure him that he has fulfilled his religious obligation. For example, if some Mujtahids consider an act to be haraam, while others say that it is not, he should not perform that act. Similarly, if some Mujtahid consider an act to be obligatory (Wajib) while others consider it to be recommended (Mustahab), he should perform it. Therefore, it is obligatory upon those persons who are neither Mujta hids, nor able to act on precautionary measures (Ihtiyat), to follow a Mujtahid.
Mujtahid is a jurist competent enough to deduce precise inferences regarding the commandments from the holy Qur'an and the Sunnah of the holy Prophet by the process of Ijtihad. Ijtihad literally means striving and exerting. Technically as a term of jurisprudence it signifies the application by a jurist of all his faculties to the consideration of the authorities of law with a view to finding out what in all probability is the law. In other words Ijtihad means making deductions in matters of law, in the cases to which no express text is applicable. (See, Baqir Sadr, A Short History of 'llmul Usul, ISP, 1984).