[535] THERE ARE THREE DOMAINS of Arabic literature, which, as sources for the sayings and doings of the Prophet, have to be considered: ḥadīth, sīra, and tafsīr. The ground-element of all three domains is the individual report, which appears in each of them in the same form, that of a pronouncement ( matn al- ḥadīth) introduced by a chain of witnesses ( isnād) . In the order, however, in which they present the enormous mass of individual reports of which they are composed, the works belonging to the three domains differ from one another. Ḥadīth collections arrange them either according to inherent points of view (as is the case with the muṣannaf works, to which the six canonical compilations, al-kutub al-sitta , belong); or according to the names of the Companions of the Prophet ( aṣḥāb or ṣaḥāba) to whom they go back in the last resort (as is the case with the musnad collections, e.g. that of Alḥnad ibn Ḥanbal). The works of sīra literature present the individual reports in chronological order of the events to which they refer; while works of the traditionalistic tafsīr literature adduce them by way of commentary on the verses of the Qur'ān to which they relate. Of course, neither all the three provinces, nor even all the works belonging to each one of them, present exactly the same material; but individual works differ much more in the choice that they make from the vast material-a choice that is determined partly by the special interests that the compilers have in mind and partly by the measure of criticism that they apply to the credibility of the individual reports. Such works, however, of any of the three categories, as are regarded as the fullest possible collections of the entire material in ḥadīth, as, for example, al-Wāqidī Kitāb al-maghāzī on the one hand and Aḥmad ibn Ḥanbal's Musnad on the other, contain in all essentials the same matter; we shall find but rarely a ḥadīth in al-Wāqidī that [536] Aḥmad ibn Ḥanbal has not cited.