The subject of study. The article examines certain aspects to realize freedom of thought and expression, as well as the acceptable limits. Freedom of thought, speech and expression issues are considered separately in the context of the religious component, its characteristics in the Islamic religion. The provisions of the main sources in the Muslim system of law – the Holy Quran and the Sunnah of the Prophet and Messenger of Muhammad (May Allah bless him) have been studied in sufficient details. The legal analysis on the issues under consideration was carried out based on doctrinal opinions, the current Russian and international legal acts, judicial practice, including the practice of the European Court of Human Rights. The article describes extremism through the prism of freedom of thought, speech and expression. It is noted that extremist activity is one of the consequences of misinterpretation, true awareness and perception of freedom of thought, speech and expression.The purpose of the study. The main purpose of the study is to clarify the origins of conflicts in the process of realizing freedom of thought, speech and expression, and substantiate the hypothesis that freedom of thought, speech and expression should have certain boundaries, especially in context of the influence of the religious factor.The methodology of the study. The study is based on a dialectical approach to the disclosure of legal phenomena and processes using general scientific methods (systemic method, logical method, method of analysis and synthesis) and special scientific methods. Among the latter there are formal legal method, linguistic method, comparative legal method, which have found their application in the legal analysis to realize freedom of thought, speech and expression.Conclusions. As a result, it is emphasized that freedom of thought, speech and expression is the achievement of modern mankind, one of the foundations of a democratic system and an element of civil society. The state-guaranteed opportunity for individuals to exercise these freedoms in society is a guarantee of a "healthy" society in the legal sense. However, as practice shows, unlimited freedom leads to its abuse, thereby infringing on the freedoms of other individuals and therefore, freedom of speech and its expression presupposes the existence of boundaries outlined by the state in the interests of society. The specifics of freedom of thought, speech and expression in the Muslim system of law based on the Holy Quran and the Sunnah of the Prophet (May Allah bless him), is that this freedom ends where the border line begins, designated by the law of the Most High.