The son has a family and his father is exhausting him with his financial demands

The hadeeth You and your wealth belong to your
father was reported by Ibn Maajah (may Allah have mercy on him) in his Sunan
from Jaabir ibn Abd-Allaah, who said that a man said, O Messenger of Allaah, I
have wealth and children, and my father wants to take all my wealth [to spend it on his
own needs] and leave nothing. The Prophet
(peace and blessings of Allaah be upon
him) said: You and your wealth belong to your father.

(In al-Zawaaid
it says: its isnaad is saheeh and its men are thiqaat according to the conditions of
al-Bukhaari).

Imaam Abd al-Razzaaq (may Allaah have mercy on
him) said in al-Musannaf:

Concerning a man who takes his sons wealth

From Aaishah who said: The Messenger of Allaah
(peace and blessings of Allaah be upon him) said: The best of what a man consumes is
what he earns, and his children are part of his earnings.

From Muhammad ibn al-Munkadir: a man referred his dispute with his
father over his earnings to the Prophet
(peace and blessings of Allaah be upon him). The
Prophet
(peace and blessings of Allaah be upon him) said: You and your wealth
belong to your father.

From Aaishah who said: A man can consume whatever he
wishes of his son’s wealth, but a son cannot consume anything of his fathers wealth
without his permission.

From Saeed ibn al-Musayyib, who said: A man can take
whatever he wants from his son’s wealth, but a son should not take anything from his
fathers wealth except with his consent.

From Ibn Jurayj, who said: Ataa did not see anything
wrong with a man taking whatever he wanted of his son’s wealth, even if it was not a case
of necessity.

Then he said (may Allaah have mercy on him):

Those who say: a man should not take anything of his son’s
wealth except with his permission.

From Ibn Seereen, who said: A son should honour his father, but
each man has more right to that which he himself owns.

Saalim reported that Hamzah ibn Abd-Allaah ibn Umar
sacrificed a camel, then a beggar came to Ibn Umar [i.e., Abd-Allaah, the
father of the one who offered the sacrifice]. Abd-Allaah said, Its not
mine [i.e., the meat of the sacrifice isnt mine to give away]. Hamzah said:
O my father, you have my permission, so give away whatever you want of it.

Ibn Qudaamah (may Allaah have mercy on him) said in his book al-Mughni,
commenting on this matter:

Any father has the right to take whatever he wants of his son’s
wealth and to take possession of it, whether the father needs it or not, and whether the
son is an adult or a child, provided two conditions are met. The first is that this should
not be unfair to the son or cause him any harm, and that the father should not take
anything that the son needs. The second is that he should not take from the wealth of one
child to give it to another child. This is what was stated by Ahmad This is because
it is prohibited for a father to show favouritism in giving to one child from his own
wealth, so the prohibition should apply even more to the case of a father taking from one
child to give to another.

Abu Haneefah, Maalik and al-Shaafa’i said:

He does not have the right to take any more from his son’s wealth than
what he needs, because the Prophet
(peace and blessings of Allaah be upon him) said:
Your blood and your wealth are as sacred to you as this day of yours in this month
of yours.

(Agreed upon). It was reported that the Prophet
(peace and blessings of Allaah be upon him) said: It is not permissible to take the
wealth of a Muslim except with his consent. (Reported by al-Daaraqutni). The son has full ownership of his wealth, and it should not be taken away from
him, as the case if he needs it . Our evidence for this is the report of
Aaishah (may Allaah be pleased with her) who said: The Messenger of
Allaah
(peace and blessings of Allaah be upon him) said: The best of what you
consume is what you earn, and your children are part of what you earn. (Reported
by Saeed and al-Tirmidhi, who said: a hasan hadeeth). Amr ibn
Shuayb reported, from his father, from his grandfather, who said: A man came
to the Prophet
(peace and blessings of Allaah be upon him) and said, My father
needed all my wealth. He said, You and your wealth belong to your
father. A longer version was reported by al-Tabaraani in al-Mujam,
and by others, which adds: Your children are among the best of your earnings, so
consume whatever they have of wealth. Muhammad ibn al-Munkadir and al-Mutlib ibn
Hantab reported: A man came to the Messenger of Allaah
(peace and blessings of
Allaah be upon him) and said: I have wealth and children, and my father has wealth
and children, but my father wants to take my wealth. The Prophet
(peace and
blessings of Allaah be upon him) said: You and your wealth belong to your
father. (Reported by Saeed in his Sunan).
Also, Allaah has described the child as a gift to his father, as He says (interpretation
of the meanings):

And We bestowed upon him Ishaaq, and (a grandson)
Yaqoob [al-Anbiya 21:72]

and We bestowed upon him Yahyaa
[al-Anbiya 21:90]

[Zakariya said:] So give me from Yourself an
heir. [Maryam 19:5]

[Ibraaheem said]: All praises and thanks be to Allaah, Who
has given me in old age Ismaaeel and Ishaaq [Ibraaheem 14:39]

Whoever is given to a person as a gift, he is allowed to take his
wealth, just as he has the right to take the wealth of his slave. (al-Mughni, part
5).

In the dissertations and fatwas of the Mufti Shaykh Muhammad ibn
Ibraaheem ibn Abd al-Lateef Aal al-Shaykh, it says the following:

A father is permitted to take from his sons wealth, because of
the sayings of the Prophet
(peace and blessings of Allaah be upon him): You and
your wealth belong to your father

(reported by the five and classed as saheeh
by al-Tirmidhi) and The best of what you consume is what you earn,
and your children are part of your earnings (reported by al-Tirmidhi,
al-Nisaa’i and Ibn Maajah from Aaishah). The fathers
taking from his son’s earnings is subject to six conditions:

1. He should not take what his child needs or the loss of which would cause
   harm to his child.

2. He should not give it to another of his children.

3. He should not take anything when either of them is on his deathbed.

4. The father should not be a kaafir when the son is a Muslim.

5. The wealth should exist in a tangible form.

6. Whatever the father takes from his son becomes his when he takes it with the appropriate
   intention or a spoken statement.

This is the gist of what our fuqaha (may Allaah have mercy on
them) have said, and this is our fatwa.