Is it permissible to revoke a financial donation to a mosque if it becomes apparent that the funds will be spent on the building's rent instead of construction, thereby causing the donor to lose the intention of a perpetual charity (Sadaqah Jariyah)?

Firstly, it is permissible to rent a building to serve as a mosque for prayer, according to the majority of scholars, in contrast to the Hanafis. The Malikis, Ibn Taymiyyah, and the Islamic Fiqh Council have affirmed the permissibility of waqf (endowment) of temporary usufruct, which is the preponderant view. Therefore, what you have done falls within the scope of waqf.

Secondly, it is not permissible for the organization to use waqf funds designated for building a mosque to rent a building, due to the necessity of adhering to the condition and intention of the endower.

Thirdly, since the agreement was for your donation to build a permanent mosque, and the organization has not fulfilled that, there is no sin upon you if you stop paying the remaining promised amount. You have the freedom to contribute to the rent if you see good in it, or to refrain and be content with what you have already paid. We advise you to look for another mosque under construction and contribute to it with the remaining amount.