This thesis focuses on the study and analysis of three main issues: 1. The role of the Qur'an in the establishment of the Sunnah, and the affirmation of its status and the importance of acting in accordance with it. 2. The role of the Prophet in the propagation and preservation of the Sunnah. 3. The main evidence that is cited by Goldziher in support of his theory of the fabrication of Hadlth during the Umayyad period. The thesis consists of an introduction, two parts and a conclusion. The introduction describes the motivation for choosing the above issues as the subject of the research and demonstrates the method followed. Part One deals with the role of the Qur'an and the Prophet in relation to the Sunnah and contains two chapters. In Chapter 1, attention is given to two issues: The clarification of the Qur'än's urgent requirement for the Sunnah from the revelation of the first verses onwards; and an examination of the Qur'än's detailed explanation of the importance of the Sunnah and of acting according to it. This chapter consists of six sections and a conclusion. Chapter 2 aims to present and discuss the various roles that were performed by the Prophet in the preservation and propagation of his Sunnah. This chapter consists of eight sections and a conclusion. Part Two, which constitutes the main part of the study, undertakes a rigorous study of Goldziher's main evidence regarding his theory of the fabrication of Hadith during the Umayyad period. It consists of an introduction, five chapters and a conclusion. In the introduction, we give a general overview of Goldziher's theory regarding the fabrication of Hadith in the Umayyad period. Chapter 3 contains an analysis of the evidence he cites in support of his claim that the Companions fabricated Iladith, and consists of five sections. Chapter 4 attempts an analysis of the evidence he cites in support of his claim that various `pious scholars' fabricated Hadith during the Umayyads' rule, and consists of seven sections. Chapter 5 contains an analysis of his evidence regarding the Umayyads' fabrication of Hadith, and consists of five sections. Chapter 6 contains an analysis of his evidence regarding the fabrication of Hadith by various theologians and consists of four sections. Chapter 7 contains a demonstration of the impact of Goldziher's opinions on subsequent studies. Finally, the Conclusion summarises the findings of the study.