All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
Waqf (Endowment) is among the acts of obedience by which a Muslim draws closer to Allah the Almighty. A Muslim offers this kind of donation in the form of an after-death continuous charity. Muslim jurists are agreed that the condition made by the Waqif (Endower) is considerable-as long as it is lawful-and it is impermissible to be violated. For example, when someone endows property in favor of his male offspring alone although it is better to include the females as well.
An-Nawawi (May Allah be pleased with him) said, "The condition of the Waqif regarding amounts of money, characteristics of recipients, and time of reception should be taken into consideration. If a person endowed a property in favor of his children and stipulated equality between males and females or favored one gender over the other, then his condition should be fulfilled….... If he said: "I endow that property in favor of my poor sons or widowed daughters, then those sons who become well off or the those daughters who remarry aren`t entitled to the endowment. But, if the sons become poor again and the daughters become widowed or divorced, then they become re-entitled to the yield of the Waqf." {Rawdat-at-Talibeen, vol.2/pp.291}.
Therefore, the condition that the daughter is entitled to the yield of the Waqf so long as she is not widowed, divorced or married remains considerable. An-Nawawi (May Allah be pleased with him) said: "This type of Waqf includes the sons of one`s sons and daughters unless the Waqif said: the sons of the sons only." {Menhaj At-Talibeen}.
If those to whom the Waqf was made gave others (sons of sons and daughters and the like) to preserve the relations of kith and kin, then they will be rewarded from Allah, but if they didn`t, then they incur no sin.
It is imperative upon whoever didn`t get a share from the yield of the endowment to be pleased with what Allah has given them for Allah is The Best Provider and Disposer of affairs. And Allah The Almighty Knows Best.