Jurisprudents of the various Islamic sects have expressed different views concerning the sources of ijtihad. Before these are examined in detail, their brief description will be in order.
1. The first view pertains to the majority of Imamiyyah jurisprudents of the Ja'fari school. They maintain that the Book, the Sunnah, ijma (consensus), and aql (reason) constitute the sources of ijtihad.
2. However, some, like the Akhbaris, who follow Mulla Muhammad Amin al‑'Astarabadi (d. 1033/1623) accept only the Sunnah as the source for derivation of ahkam.
3. Some, like the jurisprudents of the Hanafi school, regard the Book, the mutawatir Sunnah, statements of the Companions, the Companions' consensus, qiyas, istihsan and urf (custom) as the sources of ijtihad ‑ as mentioned by Abu Zuhrah in his Ta'rikh al‑madhahib al‑ 'arbaah.
4. Some others, like the ulama' of the Maliki school, followers of Malik ibn Anas al‑'Asbahi, believe these sources to be the Book, the Sunnah, consensus of the jurists of Madinah, masalih mursalah (a kind of qiyas), such statements of the Companions as are not based on ray, and qiyas mansus al‑illah. This is according to Dr. Subhi Mahmasani, in his book entitled Falsafat al‑tashri Al al‑'Islam.
5. Another group, like the Shafi'i jurisprudents, followers of Muhammad ibn Idris al‑Shafi'i, regard the Book,the Sunnah, ijma, and qiyas mustanbat al‑illah as the sources of ijtihad. This too has been mentioned in Falsafat al‑tashri fi al‑ Islam.
6. According to some others, like the ulama' of the Hanbali school, followers of Ahmad ibn Hanbal al‑Shaybani, the sources of ijtihad are: the Book, the Sunnah and the fatwas of the Sahabah when these do not contradict the Book and the Sunnah ‑ even mursal and daif traditions.
7. Some others, like the ulama' of the Zahiri school, followers of Dawud ibn 'All al‑Zahiri al‑Isfahani, restrict themselves to the Book, the Sunnah, and ijma . Furthermore, they see no scope for ijma after the era of the Caliphs. In the words of the second leader of this school,
Ibn Hazm al‑'Andalusi al‑Zahiri, anyone who claims ijma on questions arising after the period of the Caliphs makes a false statement.
It is notable that whatever has been mentioned above on the subject are not the only viewpoints; there are many others as well. For example, Ustadh Mubammad al‑Dawalibi in his book al‑Madkhal ila ilm usul al‑fiqh, describes the sources for inference of ahkam as: (1) the Book, (2) the Sunnah, (3) ijma and (4) ijtihad. This view has been accepted by Muhammad Rashid Rida, the renowned author of al‑Wahy al‑Muhammadi. Furthermore, according to that which has been ascribed to Malik ibn Anas al‑'Asbahi the sources of ijtihad comprise: (1) the
Book (2) the Sunnah (3) ijma (4) qiyas, (5) istihsan (6) the principle of istislah, (7) al‑madhhab al‑Sahabi, (8) sadd al‑dhara'i (9) fath 'al‑dhara'i, (10) qanun al‑salaf, (11) istishab, (12) istiqra' (13) bara'ah asliyyah, (14) urf, (15) istidlal, etc.
However, we will confine ourselves to the above views, proceeding to examine the impact of these different views of ijtihad and legal deduction.
It is evident that the theoretical differences about the sources of ijtihad should lead the jurisprudents, in the process of legal deduction vis‑a‑vis new problems and developments, to adopt different courses resulting in divergent fatawa. Hence we find different schools of thought in the history of jurisprudence and ijtihad.
However, of the many schools of thought, only five came to be officially recognized, namely, the Ja'fari, the Hanafi, the Maliki, the Shafi'i, and the Hanbali. With the passage of time the others have been abandoned and forgotten.
We will now discuss and examine the sources of ijtihad, one by one, in order to gain a better acquaintance with the basic sources for inferring and deducing the ahkam.
As indicated earlier in our discussion, the very first source of ijtihad is the Book. Accordingly, the subject of discussion in this article will be the Qur'an, held in common accord by jurisprudents of all schools of thought in Islam (including, besides the well‑known five, the Zahiri, Jariri, Tamimi, Nakhi, Awza'i, Thawri, Laythi, Kalbi, and other schools now extinct) as the primary source of reference for identifying the ahkam of the Shari'ah.
If any occasional difference among the schools of thought is discernible concerning the Qur'an, it relates to opinions concerning the interpretation of the verses, and other problems like naskh (abrogation), tahr'if, the criteria of amr and nahy, amm, mutlaq, etc. However, this procedural aspect does not affect the purpose of our present discussion. The Holy Qur'an represents the primary source of Divine laws and, as such, the Book has precedence over the other sources to be consulted for obtaining the ahkam of the Shari'ah. The Qur'an has been, and will remain ‑ in addition to being the comprehensive source of Divine laws ‑ the criterion for judging traditions and ahadith. It is on this very basis that from the time of the Holy Prophet (S) till now and for ever, the Book remains the primary source of reference for Islamic jurisprudents. The history of jurisprudence and ijtihad testifies to this fact. However, when this basic source is examined from the standpoint of ijtihad and legal deduction, certain noteworthy issues arise. It is invariably essential to pay due attention to such matters as fiqh al‑Qur'an (juristic study of the Qur'an), the determination of the Qur'anic verses having a bearing on legal deduction, the determination of the muhkamat and the mutashabihdt, the problem of restriction (takhsis) of the general import (amm) of the verses by khabar al‑wahid, the legitimacy of interpreting the Qur'an in the light of khabar al‑wahid, etc. These are issues that simply cannot be ignored. Their effect on the derivation of ahkam from the Qur'an, too, cannot be overlooked.
A significant number of Qur'anic verses constitute ayat al‑'ahkam (legally relevant verses). These verses have been, and are, the basis for deriving ahkam. Their number totals approximately five hundred. These were gradually revealed on various occasions during the years following the Prophet's Hijrah. Accordingly, the ayat al‑'ahkam are to be sought in the Madani verses.
The ayat al‑'ahkam lay down the Islamic laws and rules concerning social, penal and economic matters. In contrast, the Makkan verses mostly describe and prescribe doctrinal and ethical principles.
Over the centuries, the great Islamic jurisprudents have painstakingly carried out continuous research concerning the ayat al‑'ahkam, and in the course of their deductive endeavour have discovered many points of juristic and scientific interest. Many of the results of their efforts are now available to us.
To know when and by whom the first investigation into the ayat al‑'ahkam was conducted is essential for familiarity with the history and development of ijtihad. Although there is no consensus in this regard, it is worthwhile that we recall what some scholars have opined in this connection.
1. Allamah Sayyid Hasan al‑Sadr, in his esteemed work Ta'sis al. Shi'ah li al‑ulum al‑'Islamiyyah (p. 321), writes that the first book concerning ayat al‑ ahkam was written by Muhammad ibn Sa'ib al‑Kalbi (d. 146/763). This view has been endorsed by Ibn al‑Nadim in his al-Fihrist (p. 57), wherein he writes: "Al‑Kalbi's Kitab ahkam al‑Quran has been narrated by Abbas ...."
2. According to some the first research in this regard was conducted by Muhammad ibn Idris al‑Shafi'i (d. 204/819), the founder of the Shafii school. Allamah Jalal al‑Din Abd al‑Rahman al‑Suyuti (d.911/ 1505) in his Kitab al‑ awa'il accepts this, and writes: "Al‑'Imam al-Shafi'i was the first writer on the subject of ayat al‑'ahkam."
3. According to Tabaqat al‑nuhat, some scholars are of the view that the first to write on ahkam al‑Qur'an was Allamah al‑Qasim ibn Asbagh ibn Muhammad al‑Bayyati al‑Qurtubi al‑'Andalusi (304/916).
Among the aforementioned claims, the one in regard to the great Shi'i scholar Muhammad ibn Sa'ib al‑Kalbi has greater validity, since his time precedes that of al‑Shafi'i and al‑Qasim ibn Asbagh al‑Bayyati. That which has been claimed by al‑Suyuti appears to signify his intention to mention the first Sunni writer on ayat al‑ ahkam. .
From among the Sunni ulama', 'Ali ibn Mush al‑Qummi (d. 305/ 917) from the Hanafi school, Abu Ishaq Isma'il ibn Ishaq (d. 282/895) from the Maliki, and Abu Yala Kabir (d. 458/1066) from the Hanbali, appear to be the first researchers in this field.
For acquainting ourselves further with the historical background of the subject under discussion, it seems appropriate that we list the important writings on ayat al‑ ahkam by ulama' of Islam.