We have indicated that the Ḥadīth transmits the sunna, the tradition or practice of the Prophet, and even if a ḥadīth is not in itself true, it may still transmit sunna; it may illustrate what the Prophet would approve of, or what he might have said had he been asked.
The preservation of the sunna has been Islam's way of maintaining its historical continuity, its link with the Apostolic period. One of the important ways this has been done is by the study and criticism of the Ḥadīth.
The following essay is by the fourteenth-century savant and historian ‘Abd al-Rahmān Ibn Khaldūn (died A.H. 808/A.D. 1406), a Spanish Arab of Tunis, who was a professor of Ḥadīth and jurisprudence as well as a historian, statesman and diplomat. It serves to illustrate the categories within which the religious scholars have operated, and the way in which they have conceived their task.
The sciences concerned with Prophetic traditions (ḥadīth) are numerous and varied. One of them concerns abrogating. The permission to abrogate previous statements and the occurrence of abrogation have been established. . . . God said: "Whenever We abrogate a verse or consign it to oblivion, We bring one that is better, or as good." (Sūra 2:100)
Two traditions may be mutually exclusive, and it may be difficult to reconcile them. . . . If in such a case it is known that one is earlier than the other, it is definite that the later abrogates (it).
This is one of the most important and difficult of the sciences of tradition. Al-Zuhrī said: "It has been a baffling and impossible task for the jurists to distinguish traditions of the Messenger of God abrogating others from those that were abrogated by them."
Another of the sciences of tradition is the knowledge of
the norms that leading Ḥadīth-scholars have invented in order to know the chains of transmitters, the (individual) transmitters, their names, how the transmission took place. . . . (The student may verify the tradition) by scrutinizing the chains of transmitters. For that purpose one may use such knowledge of the probity, accuracy, thoroughness and lack of . . . negligence as the most reliable Muslims describe a transmitter as possessing. . . .
The highest grade of transmitted material is called "sound" (ṡaḥīḥ) by the scholars. Next comes "good" (ḥasan). The lowest (acceptable) grade is "weak" (ḍa‘īf). The classification includes also "skipping the first transmitter's name" (mursal), "omitting one link" (munqaṭi‘), "omitting two links" (mu‘ḍal), "affected by some infirmity" (mu‘allal), "singular" (shādhdh), "unusual" (gharīb) and "singular and suspect" (munkar). In some cases there is a difference of opinion as to whether (traditions so described) should be rejected. In other cases there is general agreement that (they should be rejected). The same is the case with (traditions with) sound chains. In some cases, there is general agreement as to their acceptability and soundness, whereas in other cases, there is difference of opinion. Ḥadīth scholars differ greatly in their explanations of these terms.
Then there follows the discussion of terms applying to the texts of the traditions. A text may be "unusual" (gharīb), ambiguous (mushkil), "affected by misspelling or misreading," "containing homonyms" (muftariq) or "containing homographs." . . .
The purpose of the discipline is a noble one. It is concerned with the knowledge of how to preserve the traditions (sunna) . . . until it is definite which are to be accepted and which are to be rejected.
The Companions of the Prophet and the men of the second generation who transmitted the Sunna were well known in the cities of Islam. There were transmitters in the Hijāz, in al-Baṡra and al-Kūfa, and then in Syria and Egypt. They were famous in their time. The transmitters of the Hijāz had fewer links in their chains of transmitters (than others) and were sounder because they were reluctant to accept (as reliable
transmitters) those who were obscure and whose conditions were not known.
At the beginning, knowledge of the religious Law was entirely based on (oral) tradition. It involved no speculation, no use of opinion, and no intricate reasoning. . . . Mālik wrote the Muwaṭṭa’ according to Ḥijāzī tradition, in which he laid down the principal laws on the basis of sound, generally agreed upon (material). He arranged the work according to juridical categories.
There was Muhammad ibn Ismā'īl al-Bukhārī, the leading Ḥadīth scholar of his time. In his Musnad al-Ṡaḥīḥ . . . he published the orthodox traditions according to subject. He combined all the different ways of the Ḥijāzis, Iraqīs and Syrians, accepting the material on which they were all agreed but excluding material concerning which there were differences of opinion. . . . His work thus comprised 7,200 traditions of which 3,000 are repeated. In each chapter, he kept separate the rescensions with the different chains of interpreters belonging to them.
Then came the imām Muslim b. al-Hajjāj al-Qushayrī. He composed his Musnad al-Sahib in which he followed al-Bukhārī in that he transmitted the material that was generally agreed upon. . . .
Scholars have corrected the two (authors), noting the cases of the sound traditions not included in their works.
Abū Dawūd al-Sijistānī, Abū ‘Isa al-Tirmidhī, and Abū ‘Abd al-Rahmān al-Nasal wrote works that included more than merely "sound" traditions. Their intent was to include all traditions that fulfilled amply the conditions making them actionable traditions . . . to serve as a guide to orthodox practice.
These are the collections of traditions that are used as reference works in Islam. They are the chief orthodox works on traditions. [Ibn Khaldūn does not mention the Sunan of Ibn Mājā (died A.H. 271/A.D. 886), usually considered the sixth orthodox work.--ED.] Other collections have been added to these five. At this time traditions are no longer published nor are (the publications of) traditions of former scholars corrected. Common experience attests that these numerous religious
men, close to each other in time, were too capable and too firmly possessed of independent judgment to have neglected or omitted any tradition, so it is impossible that some later scholar might discover one. At this time one is concerned with correcting the principal written works and fixing the accuracy of their transmission. . . .
Al-Bukhārī s Ṡaḥīḥ occupies the chief place among them 42
91:42 Ibn Khaldūn, The Muqaddimah (New York, 1958), translated by Franz Rosenthal, Vol. II, pp. 447-457, passim.