As we know, the tradition or ahadith of the Holy Prophet (S) recorded in the books of Muslim traditionists begin with chains of transmitters on whose authority the traditionist reports the Prophet's acts or statements. Experts of hadith amongst Muslims have developed certain criteria for assessing the reliability of different chains of transmission and ascertaining the authenticity of the contents of traditions. They have developed a terminology with terms denoting various classifications of hadith depending on the character, strength or weakness of narrators and other factors, such as mutawatir, ahad, sahih, hasan, qawi, da’if, etc.
By tawatur is meant the multiplicity of the sources of a certain report that leads to certitude in the listener that the report is indeed true. One's knowledge of the existence of distant countries and towns and such historical figures as Cyrus or Napoleon may be said to be based on the tawatur of reports that one hears about them. So also is one's knowledge of the contemporary events not witnessed by him.
A mutawatir hadith is one which has been reported by so many different chains of transmission and such a number of narrators in every generation as normally could not agree to fabricate a tradition without the fact of its fabrication becoming known. Although some jurisprudents have specified a particular minimum for the number of narrators, such as five, seven, ten or even hundred, it is generally held that no particular number can be specified and the number capable of producing certitude depends on the experience of the listener.
Islamic jurisprudents have set forth certain conditions for a tradition to be mutawatir. Al-Ghazali in al-Mustasfa min ‘ilm al-usul 1 mentions the following conditions.
(1) That the transmitters should report on the basis of knowledge (‘ilm) and not conjecture (zann).
(2) Their knowledge should have been acquired through the senses.
(3) That the number of narrators should be sufficient to produce certitude.
(4) That all the links in the chains of transmission of a report should fulfill the first two conditions and their number in every stage of transmission must fulfill the third condition.
Al-Shaykh al-Hasan ibn Zayn al-Din, the Shi’i author of Ma’alim al-usul, mentions similar conditions for a report to be mutawatir. As can be seen, the legal condition of ‘adalah (justice) is not required for the narrators nor are they required to be thiqah when the conditions of tawatur are fulfilled. Rather, al-Ghazali states explicitly that in such cases knowledge is attained even if the narrators should be fasiq. The author of Ma’alim states two conditions in order for a mutawatir report to produce knowledge in the listener:
(1) The listener should not have previous knowledge of the matter, for it is not possible to know something that one already knows.
(2) The listener should not be inhibited by doubt or imitation (taqlid) in his belief, for then the report will fail to make any impression upon him.