This paper examines fiqh manuals and fatwas addressing the dramatic increase in the number of Friday mosques in Cairo and Damascus under the Mamluks, who ruled between 1250 and 1517, when a series of new Friday mosques were built and new religious complexes including madrasas and khanqahs started being used for Friday prayer. These new Friday mosques changed the urban character of both cities and generated heated debates amongst the ulama in support of or opposition to their presence. This illustrated paper explores the meaning and function of Friday mosques through examining a collection of legal opinions (fatwas) by the 14th century Sunni jurist Taqi al-Din al-Subki (d. 1355). Al-Subki’s elaborate fatwas trace the historical development of Friday mosques from early Islam until his time focusing two interrelated issues: 1) the location, space, and adjacencies of the Friday mosque, focusing on the permissibility of multiple Friday prayers in one city; and 2) the role of the waqf of minbars in changing the nature of Friday mosques. While the historical impact of waqfs on the building, expansion, and support Friday mosques has been well researched, their role in changing the nature and number of Friday mosques has received less attention. As a chief judge, a celebrated jurist, and a mufti who lived and worked in both cities, al-Subki presents a clear explanation for the limited presence of Friday mosques before the Mamluk period and the increase in their numbers that made them an architectural and visual symbol of Islam since then.