Can he take back the zakaah of his wealth if he gave it to a poor person then found out that he did not need it?

Praise
be to Allah

Firstly:

It is
permissible to give zakaah to a sick person to spend on his medical
treatment, if he cannot afford that. Please see the answer to question no.
105328.

Secondly:

If someone gives
his zakaah to someone who he thinks is poor or in need, then he finds out
that he is well-off or is not in need, or that the poor person was able to
save something of that (zakaah) money, then the giver has done his duty and
he has no right to take back his zakaah.

It says in
Zaad al-Mustaqni‘: If he gives it to someone who he thinks is not
entitled to it, then it turns out that he is entitled to it, it is not
regarded as zakaah except in the case of his giving it to a well-off person,
thinking that he is poor. In that case it is acceptable (as zakaah).

For example, a
man came asking for help and he appeared to be poor, so I gave him some
zakaah. Then someone else came to me and said: What did you give him? I
said: Zakaah. He said: This person is better off than you. In this case it
is still valid, because we judge on the basis of what appears to be the
case. An example of that is those who ask for help in schools and mosques,
then we give to them on the basis of how they appear to be.

The evidence for
that is the story of the man who gave charity one night. He went out with
his charity and gave it to someone, and in the morning the people started
saying: Last night charity was given to a rich man. He said: Praise be to
Allah for a rich man, thinking that it was a serious mistake. Then he went
out again and gave charity to a prostitute, and in the morning the people
started saying: Last night charity was given to a prostitute. He said:
Praise be to Allah for a rich man and a prostitute. Then he went out a third
time and gave charity that ended up in the hands of a thief, and in the
morning the people started saying: Last night charity was given to a thief.
He said: Praise be to Allah for a rich man, a prostitute and a thief. It was
said to him: As for your charity, it has been accepted. As for the rich man,
perhaps it will be a reminder to him and he will give in charity. As for the
prostitute, perhaps she will no longer need money and so she will refrain
from adultery. As for the thief, perhaps  because what you gave him will
suffice him and he will refrain from stealing. So his actions became useful
and acceptable to Allah, and beneficial to those to whom he gave charity.
From this it may be understood that if someone gives charity to a poor
person and he turns out to be well-off, then it is still acceptable.

Some of the
scholars are of the view that if he gives it to someone who he thinks is
entitled to it after examining his case, then it turns out that he is not
entitled to zakaah, it is still valid, even if he is not well-off. In other
words, that applies in all cases, because the giver feared Allah as much as
he could and tried his hardest to find out about the recipient of his
charity, and Allah, may He be exalted, says (interpretation of the meaning):
“Allah
does not charge a soul except [with that within] its capacity”
[al-Baqarah 2:286].

What matters
with regard to acts of worship is what the accountable person thinks is the
case. This is in contrast to interactions with other people, where what
matters is what really is the case. It is difficult for us to tell him that
his zakaah is not acceptable, even though he tried his best to find out what
the situation was, and the one who makes the effort to find out will receive
one reward even if he is mistaken; if he gets it right then he receives a
double reward.

This view is
more likely to be correct: if he gave it to one who he thought was entitled
to receive it after studying his case, then it turned out that he was not
entitled, his zakaah is still valid, because as it is proven that it is
valid if he gives it to a well-off person thinking that he is poor, then the
same applies in the case of other categories.

End quote from
ash-Sharh al-Mumti‘ (6/264).

Thus we may
conclude that your zakaah was valid, praise be to Allah, and you do not have
to ask for any of it to be returned.

Thirdly:

It is not right
for the one who is in need or the one who is taking care of him to take more
than he needs, when he knows that it is zakaah money, and he should not
accept (anything surplus to his needs), because of the general meaning of
the words of the Prophet (blessings and peace of Allah be upon him)
concerning zakaah: “The one who is well-off and the one who is strong and
able to earn a living has no share of it.” Narrated by Abu Dawood (1391) and
an-Nasaa’i (2551). Classed as saheeh by al-Albaani in Saheeh Sunan Abi
Dawood.

The words
“Zakaah is not permissible for a rich person, or for one who is strong and
healthy” were narrated by Abu Dawood (1392), at-Tirmidhi (589), an-Nasaa’i
(2550) and Ibn Maajah (1829); classed as saheeh by al-Albaani in Saheeh
Sunan an-Nasaa’i.

Its says in
Mataalib Ooli an-Nuha (2/259): If zakaah is given to someone who is not
entitled to it because the giver was unaware of his situation, then the one
who took it must give it back. End quote.

The scholars of
the Standing Committee were asked: A widow is asking: I still have some of
the charity money that was given to me, and also some zakaah money. One full
year has now passed (since it was given to me); do I have to pay zakaah on
it, and if I have to pay zakaah on it, how should I do so?

They replied: It
is not permissible for this woman to take zakaah more than she needs. With
regard to the money that she has, if it reaches the minimum threshold and
one full year has passed, then she must give zakaah on it, at the rate of
one quarter of one tenth, which is equivalent to 2.5%.

End quote from
Fataawa al-Lajnah ad-Daa’imah, vol. 2 (8/381).

As your paternal
aunt has died, and this money is left in the possession of her daughters, if
they knew that their mother was not entitled to zakaah, or she took more
than she needed, knowing that the money was zakaah money, then to be on the
safe side it is more prudent for them to dispose of this money by giving it
to the poor and needy.

If they included
it in the estate and divided it, then there is no blame on them. Because the
money was unlawful due to the manner in which it was acquired, it was
unlawful only for the one who acquired it, and it may be inherited from that
person when he died, according to the more correct scholarly view.

If the mother
was not aware that it was zakaah money, or she was aware of that but she
took only as much as she needed, or what she thought she needed, then some
of it was left over, then there is no sin on her, and what she left behind
is for her heirs.

And Allah knows
best.