Assalaamu alaykum wa rahmatullaahi wa barakaatuh. A sister is asking a question regarding Zakah. My mother died a few years ago, leaving behind some money for my unmarried sister, who was not married, and my mother's intention was to leave some money for her so that when she gets married, she can use that money. However, I realized after some time that my sister was careless regarding affairs of money and that she has the habit of spending more then what she has, and as a result, she developed the habit of borrowing large amounts of money from others. After looking into this matter, I decided to buy a piece of land from that money which my mother left for her, so that I can save it for my sister, and I also had the intention that if she would die (my sister), I could sell the land and return her debts to all those whom she borrowed from. Please remember that my sister does not know about this piece of land, because if she know about it, she will sell it and also spend it with extravagance. I live abroad, and I am concerned about her. I visit my homeland and try to pay her debts as much as I can, but the amount of her debts is too many, and she owes so many people that I cannot pay it all. My sister is very careless in repaying it. My question is: do I have to pay zakah on this piece of land which belongs to my sister, as she does not know about it?
Second question: if I pay zakah on it every year and save half of the zakah for one of my cousins who is minor and an orphan, is that allowed? Can I give half of the zakah to my sister (to whom that land belongs, but she has no source of income other then myself and my brother, and we are not able to fullfill her needs, as she spends a lot); is that possible?
Third question: if I save half the zakah for that orphan girl and this amount reaches the Nisaab (minimum amount liable to zakah), do I have to take zakah from that money too though this money is already zahah in the first place?
Please answer me soon, as I worry about these matters.

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.

Apparently, the sum of money that your mother left for your sister is considered a "will"; that is, if your mother did not give her possession of this money in her lifetime or left it with a trustee (guardian) if your sister was still young; in which case, it would be a "will for an heir", which is invalid unless all the other heirs approve of it.

Ibn Qudamah said, “If a person makes a will for his heir and the other heirs did not approve of it, then it is invalid, without any disagreement among the scholars in this regard. Ibn Al-Munthir and Ibn ‘Abd Al-Barr said, ‘The scholars agreed in consensus on this matter.’”

So if the other heirs object to this will, then it is invalid and the money must be divided among all the heirs, because it is part of the inheritance.

Assuming that the will is approved by all the heirs, then it becomes the property of your sister. It is not permissible for you to dispose of her money by buying land. In principle, it is not permissible to dispose of the money of a Muslim without his permission; this purchase is called the Fudhooli purchase (unauthorized purchase), which is a matter of difference of opinion among the scholars. Some scholars said that it is valid if the sister who owns the money agrees, while some others said: the purchase is considered null and void.

The Kuwaiti Fiqh Encyclopedia, when mentioning the statements (of the scholars) in this regard, reads:

“One of the views is that of the Maaliki School and of (Imaam) Ahmad in one of his narrations: It is that the Fudhooli purchase is like the Fudhooli sale; its effectiveness depends on the approval of the one for whom he purchased it. If the one for whom it is purchased approves it, it is effective, and if he refuses it, then it is void.

The second view is that of the Shaafi'i School in its new opinion and the Hanbali School in its preponderant opinion: It is that the Fudhooli purchase is invalid, and it does not entail any ruling or effect.”

Therefore, you are now obliged to tell your sister the truth about this matter. If she agrees to approve the purchase, then it is valid and the land remains her property and she is responsible for disposing of it according to the view that the purchase in this case is valid.

With regard to paying the zakaah on this land – if zakaah is obligatory– then it is obligatory on the sister who owns the land, and it is not permissible to pay the zakaah without her permission because of the lack of intention (i.e. zakaah requires intention). As for paying her debts, it is permissible to pay them without her permission.

Shaykh Ibn 'Uthaymeen said in Fataawa Noor ‘ala Ad-Darb:

“Whoever pays zakaah on behalf of another without his permission, then it is not sufficient in clearing that person of their liability, because one must have the intention to pay zakaah, and it is not like paying a debt. In regard to paying a debt, if you pay a debt on behalf of someone else without his permission and you intend to ask him to give you the amount you paid, then you can do so. With regard to zakaah, it is not valid to pay zakaah on behalf of a person without him entrusting you to do so, because zakaah is an act of worship that requires the intention from the one who must pay it. Therefore, if he did not entrust you with paying it, then you have paid the zakaah on his behalf without any intention from him, so it is not valid, as the Prophet said, ‘Indeed, actions are judged according to their intentions, and every person will get the reward of what he has intended.’”

If we assume that the sister who owns the money is foolish, then she may be prevented from disposing of her property, but this prevention (Hajr, i.e. interdiction to use one's own property due to some Shariah reasons) can only be carried out by the order of an Islamic court. Ibn Qudaamah said, “Ibn Al-Munthir said, ‘Most of the scholars are of the view that every person who wastes his wealth is to be prevented from disposing of it, whether he is young or old.’”

The Kuwaiti Fiqh Encyclopedia reads, “The majority of jurists who are of the view that a person who is foolish is prevented from disposing of his wealth are also of the view that this can only be done by the order of the judge. Also, cancelling this Hajr must be done by the order of the judge, because since the Hajr was by order of the judge, it cannot be overruled except by his order. Also, the person's level of maturity needs to be examined, and also whether he has stopped wasting his money or not; so it is similar in this regard to preventing him from spending.”

As for the remaining questions related to the zakaah on the land, then there is no need to ask them now because you are not required to pay the zakaah on this land, and it is not permissible for you to pay the zakaah on behalf of your sister without her permission while she does not even know about the land, as you mentioned.

Allah knows best.