The article below explains the qualifications one must have to become a Mujtahid (Scholar) (One who strives to do Ijtihad) according to various classical scholars.
The earliest complete account of the qualifications of a Mujtahid is given in Abu’ Husayn al-Basri’s (d. 436/1044) al-Mu’tamad fi Usul al-Fiqh. The broad outline of al-Basri’s exposition was later accepted, with minor changes, by al-Shirazi (d. 467/1083), al-Ghazali (d. 505/1111) and al-Amidi (d. 632/1234). This does not mean that the requirements of Ijtihad received no attention from the Ulema who lived before al-Basri, however they did not see it necessary to lay down the conditions for Ijtihad in this manner.
The Hanafi jurists, Fakhr al-Islam ‘Ali b. Muhammad al-Bazdawi (d.483 A.H.) and `Ubaydullah ibn Mas’ud Sadr al-Shar‟iah both stated that to perform Ijtihad a jurist should have knowledge of the Qur‟an together with its meaning, dictionary and legal, and its various divisions, of the traditions (Hadith) including the texts and authorities thereof, and of the rules of analogical deduction (Qiyas).38
The following are the qualifications needed to perform Ijtihad, these qualifications are derived from the definition of Ijtihad which is based on specific evidences as explained earlier:
A. The Mujtahid must be a Muslim male or female of sound mind who has attained a high level of intellectual competence.
B. Since the text of the Qur‟an and Sunnah were revealed in the Arabic language, Ijtihad can only be performed based on the Arabic text. One must have knowledge of the Arabic language to the extent that it enables a correct understanding of the Qur‟an and the Sunnah. A complete command in Arabic is not a requirement for some kinds of Mujtahideen, but the Mujtahid must, at least, know the fine points of the language related to the subject at hand. He must also be able to comprehend the sources accurately and deduce the rule from them. He should know enough by which he can understand the circumstances of the Arabs, the current customary usage in their speech such that he can distinguish the textual indications (Dalaalat al-alfaaz) in terms of the following: congruence (Mutaabaqah), inclusivity (Tadmeen), requisite (Iltizaam), Mufrad (singular), Murakkab (construct), comprehensive (Kulli), partial (Juz‟i), Haqeeqah (literal), Majaaz (metaphorical), homonym (Ishtiraak), synonym (Taraaduf), uttered meaning (Mantuq) and implied meaning (Mafhum) etc.
C. The Mujtahid also needs to be knowledgeable of the Qur‟an, the Makki and Madani contents of the Qur‟an, the occasion of their revelation (Asbab al Nuzul) and must have a full grasp of the legal contents of the Qur‟an, but not necessarily of the narratives and parables of the Qur‟an and its passages relating to the Hereafter. The knowledge of the Ayat ul Ahkam (verses regarding rules) includes knowledge of the related commentaries (Tafsir) with special reference to the Sunnah and the views of the Sahabah (ra) related to the subject at hand. According to some Ulema, including al-Ghazali, Ibn al-Arabi, and Abu Bakr al-Razi, the legal ayat of the Qur‟an which the mujtahid must know amount to about five hundred. Shawkani and others, however observe that a specification of this kind cannot be definitive.
D. The Mujtahid must possess an adequate knowledge of the Sunnah, especially the part relating to his Ijtihad and be familiar with the rulings in the Sunnah. The Mujtahid must also know the incidents of abrogation in the Sunnah and the reliability of the narrators of Hadith.
E. He must have knowledge of Usul al-Fiqh so that he will be acquainted with the procedures for extracting the rulings from the text and the implications.
F. The Mujtahid should be aware of the opinions of different Mujtahideen, if any exist. It is essential for a Mujtahid to be familiar with the Daleels of other Mujtahideen, on a particular issue as how the other Mujtahid understood the Daleel and the issue.
G. Finally, he must have a comprehensive knowledge of the issue on which Ijtihad is being performed. To extract any ruling one has to understand the subject thoroughly. If the Mujtahid does not understand an issue, he is not allowed to do Ijtihad regardless of where he lives. To understand the issue, the Mujtahid can go to experts. For instance, there might be an issue in genetic engineering. To understand the process of genetic engineering, the Mujtahid can go to an expert in this field.
Therefore, these criteria are enough to qualify one to do Ijtihad, and it is incorrect to say that each issue requires the Mujtahid to reside in that environment.
The Mujtahid can reside anywhere and do Ijtihad as long as he is familiar with the issue being dealt with. If the Mujtahid is not familiar with the issue, he is not allowed to do Ijtihad, even if the issue occurs in the same environment that the Mujtahid is residing in.
Extract from Understanding Usool ul-Fiqh by Abu Ismaeel and Abu Tariq Hilal