The article is devoted to issues of systematization of the main sources of Islamic law. The research draws readers’ attention to the history of compilation and systematization of the texts of the Quran and the Sunnah (Prophet’s tradition), which became essential sources for Islamic law. The author distinguishes two periods of this systematization. The first began in the lifetime of Prophet Muhammad. It is characterized by the partial record of the main sources of Islamic law. In this period, the Quran was written down completely, but not systematized. As for the Sunnah, just a little of it was recorded. The second period began with Khalifah Abu Bakr: the systematization and standardization of the Quranic texts continued, while Hadith were communicated verbally. Systematic collection of Hadith began in the late 7th century. Their first written collections appeared in the early 8th century. All this helped to prepare the source base of Islamic law.