How do we know what we know about Islamic history? ‘The sources’ attempts to answer this question. The documents of Cairo Geniza, which record daily life amongst ordinary people and provide a richly detailed snapshot of Islamic history in the 11th to 13th centuries, and Yemeni Quranic fragments dating from the late 7th and early 8th century, which provide some of the earliest hadiths, or traditions about Muhammad, are considered. The authenticity of recorded hadiths, isnad-analysis, and ‘hagarism’ are discussed. Almost every work of fundamental importance to classical Islamic law, theology, Quranic and hadith studies, and historiography dates from the 800–1100 period.