Buying and selling is one of the main economic institutions in Islamic Law. It allows people to exchange goods and services in accordance with the principles of fairness and equality. The article examines the scientific method of making decisions by the founder of the Shafiʻi legal school, the famous thinker of the early Middle Ages Imam al-Shafiʻi (767–820), and analyzes his views in the field of law, which the Shafiʻis refer to in their relationships in the trade transactions. Particular attention is paid to the issue of sources of Islamic Law the Shafiites appeal to. In this article, for the first time in Russian jurisprudence, the author studies and examines in sufficient detail the Shafiʻi approach to purchase and sale. In addition, the authors takes as the focal point the compromise nature of the Shafischool, which, on the basis of exclusively scientific methods, managed to synthesize the most promising provisions of more “liberal” Hanafism and “conservative” Malikism.