Impermissibility of revoking Waqf of land dedicated to be a Masjid

Q: His Highness Prince `Abdul-Rahman ibn `Abdullah Al Sa`ud promised to grant a free piece of land in Al-Dabi`ah town for building a school on. However, carrying out the promise of the prince is conditional on the permissibility of the latter's withdrawal of a previous promise of granting the same land for constructing a `Eid Masjid (a large mosque where the Festival Prayer is held) on. His Highness asked us to consult scholars regarding that matter; does he have to choose granting the concerned land for the `Eid Masjid to fulfill his earlier promise or grant it to the Ministry of Education for building a school on? It may be worth mentioning that there is currently a Masjid (mosque) for Salat-ul-`Eid (the Festival Prayer) at the west of Al-Dabi`ah.

A: If His Highness, Prince `Abdul-Rahman ibn `Abdullah Al Sa`ud, has actually granted the concerned land for building a `Eid Masjid, it has to be allocated for that purpose and His Highness is not permitted to withdraw his grant. However, if he has (Part No. 16; Page No. 94) only given a mere promise to grant the land for building a Masjid on; it is preferable for him to fulfill this promise. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.