In the absence of reliable archaeological evidence, the question of how the Prophet’s mosque was made represents a real challenge. Its origin remains moot despite many attempts to settle the question. While the structure built by the Prophet in Madina, soon after the Hijra, is believed by many to have been the prototype of the mosque, the currently dominant theory that it was only a ‘house’ has cast doubt on that belief. The building was traditionally known as the ‘Mosque of the Prophet’ until Caetani, followed by Creswell et al., theorized that it could not have been a place of worship in the time of the Prophet, mainly because of the nature of the non-sacred activities it is reported to have accommodated and also because of the non-specific use of ‘masjid’ in the Qurʾān. This paper evaluates the Caetani–Creswell theory and the responses to it by Western and Muslim scholars. It explains why the whole question needs to be revisited, what conceiving the building as a ‘house’ or a ‘mosque’ means in terms of a number of undecided issues such as the immediate origin of the mosque and the kind of impulses that shaped its design. The paper goes on to examine, mainly from Qurʾān and ḥadīth, which of the two designations, ‘house’ or ‘mosque’, should be accepted and why. In particular, it investigates whether early Islam, within the framework of the Qurʾān and the teachings and practices of the Prophet, could have provided the necessary prompts for the making of the mosque and the shaping of its essential functional and architectural elements.