If money donated for the purchase of land for a mosque is not ultimately used for that purpose, is it permissible to reclaim the donated funds? And donate them instead for the purchase of land for another mosque? Please provide references.

All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger.

There is no Islamic objection to taking back money that was donated to buy land for a mosque and then donating it toward buying land for a different mosque.

The basis for this is that a waqf (endowment), although binding and in principle not to be disposed of, may be exchanged when there is a benefit in doing so. Indeed, exchanging it becomes obligatory if its benefits have ceased. A charitable donation (sadaqah) is all the more deserving of this ruling.

Shaykh Al-Islam Ibn Taymiyyah said in Al-Fatawa Al-Kubra: "When there is a need, it is obligatory to exchange a waqf for its equivalent; and without a need, it is permissible to exchange it for something better, because the benefit is evident." [End quote]

He also said: "Ahmad Ibn Hanbal permitted replacing one mosque for another for the sake of benefit, just as he permitted altering it for the sake of benefit. He argued that 'Umar Ibn Al-Khattab replaced the old mosque of Kufa with another mosque, and the first mosque became a market for date-sellers. Ahmad also permitted, if the place has fallen into ruin, that the mosque be moved to another village. Indeed, according to the more apparent of the two narrations from him, it is permissible for that mosque to be sold and another mosque built with its proceeds in another village, if the first village has no need of it." [End quote]

Allah Knows best