Criticism of Hadith thus provides "certainty of knowledge" of what Muhammad said, in fact it is only the much rarer subset of sahih -- "mutawatir" hadith -- that provide certain knowledge. "Mutawatir" means the report "of a large number of narrators whose agreement upon a lie is inconceivable. This condition must be met in the entire chain from the origin of the report to the very end." However, according to Wael Hallaq, "the bulk of hadith with which the traditionists dealt, and on the basis of which the Jurists derived the law" were known as "ahad" — i.e. non-"mutawatir" hadith; Hadith without "textually
Introduction to the Science of Hadith authored an abridgement: The following have set "Introduction" to verse, adding some content in the process: The numerous editions of the "Introduction" in its original Arabic include two of the more reliable: The "Introduction" has been translated into English and published as "An Introduction to the Science of Hadith", by Eerik Dickinson, as part of the Great Books of Islamic Civilization series. The translator has provided a biography of Ibn al-Ṣalāḥ derived from numerous sources, in addition to copious footnotes throughout. It is published by Garnet Publishing Limited, Reading, 2006, 356 pgs. Introduction to the Science of Hadith (Ibn al-Ṣalāḥ's)