The article introduces the content of one of the little-known lifetime published works of an outstanding Tatar religious thinker Musa Jarullah Bigiev (1875-1949), which is devoted, in particular, to the study and disclosure of the meaning of the Quranic concept of Yajuj-Majuj. The facts from the biography of the scientist introduced into the scientific circulation provide a full disclosure of particular reasons for the appearance of the work under consideration. The research by M. Bigiev is based on a deep source study, on the results of comparative linguistics and cultural-historical analysis including religious books of Judaism, Christianity and Islam. The author considers the inadmissibility of introducing the pre-Islamic ideas about the concept of Yajuj-Majuj into Islamic exegetics, and a number of other concepts that are accepted to be among the common heritage of Abrahamic religions; the paper emphasizes extreme importance of free thought; it draws attention to the role of Turks in the world history in its past, present and future; it makes a number of interesting inferences into the hidden meaning of a Quranic story about Yajuj-Majuj.