Is it permissible to dedicate part of one's property as an endowment (waqf) for the purpose of spending on parents and unmarried sisters, and then for it to become an ongoing charity (sadaqah jariyah) or to revert to the heirs after the death of the parents and the marriage of the sisters, and is zakat obligatory on the endowment?

The issue of stipulating a time limit for an endowment (waqf) and an endowment made to a non-existent entity is a matter of disagreement among jurists.

The Hanafis, Shafi'is, and Hanbalis, in one opinion, held that it is not permissible to set a time limit for an endowment, while the Malikis, and in another opinion, the Shafi'is and Hanbalis, permitted it.

In the case where the beneficiary of the endowment ceases to exist, opinions also differ: - The Hanafis stipulate that the final beneficiary of the endowment must be an entity that does not cease to exist. - The Malikis differentiate between a perpetual endowment and a temporary one. The former reverts to the closest poor relatives of the endower, while the latter reverts to the endower or their heirs. - The Shafi'is have two opinions regarding the validity of the endowment when the beneficiary ceases to exist, and the more prevalent opinion is that it remains an endowment. - The Hanbalis hold that the endowment remains valid and its proceeds are disbursed to the endower's heirs.

The condition stipulated by the endower that the income from the endowment, after their parents and sisters, be spent on an ongoing charity (sadaqah jariyah) or revert to their heirs, is considered valid by some scholars.

Regarding the zakat on endowed wealth: - The Hanafis and Shafi'is do not consider it subject to zakat because it has ceased to be owned by the endower. - The Malikis consider zakat obligatory on the endower because it remains their property. - The Hanbalis differentiate: if the endowment is for a specific person, zakat is obligatory on them; if it is for an unspecific entity, there is no zakat on it.

Ibn Uthaymeen held that there is no zakat on real estate endowments, nor on their income if they are for a charitable cause, because they do not have a specific owner.