The descendants of the Prophet Muhammad inherited his charisma and sacred prestige. These properties were shared by his descendants who became the legendary Muslim saints and scholars, also in Central Asia and Siberia, and whose names are connected with the early history of the Islamization of the Siberian Tatars. New manuscripts of a genealogical treatise, which is the main topic of this article, the Shajara risālasī, were recently discovered. An edition (with variant readings) of the Tatar text and an English translation are here offered for the first time. Yasaviyyan influence in Siberia was known to have existed as early as the 17th century. However, critical reading of the genealogical treatise makes it possible to trace back the islamization of the Siberian Tatars by one century. Bukhara and Urgench could be identified as the centres from where this islamization drive of Siberia was launched. The sacred genealogies circulated for about four centuries in the common intellectual space of Central Asia, Eastern Turkestan, Siberia and the Volga-Ural region, untill the Bolshevik reign brought all this to an untimely end.