Hadith are "expressed in Muhammad's words", whereas the latter are the "direct words of God". A "hadith qudsi" need not be a "sahih" (sound hadith), but may be "da‘if" or even "mawdu‘". An example of a "hadith qudsi" is the hadith of Abu Hurairah who said that Muhammad said: When God decreed the Creation He pledged Himself by writing in His book which is laid down with Him: My mercy prevails over My wrath. In the Shia school of thought, there are two fundamental viewpoints of Hadith: The Akhbari view and the Usuli view. The Usuli scholars stress the importance of
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)