I engaged in some trade, and I promised to give a certain amount of the profits for the sake of Allaah. My question is:

 Can I spend this amount on the marriages expenses of my brother, cousins and relatives, because they are not well-off? Is it essential to tell them that this is charity? Can I give some of it to a needy relative even if he is one of those who want to show off in their wedding and spend extravagantly even if they are in need?.


Praise be to Allaah.
 

You have to
fulfil your promise of spending a specific amount for the sake of Allaah. If
you intended or specified a particular area then you have to spend the money
in that way, and not in any other. If you did not intend or specify a
particular area, then you have the choice of spending it in whatever
charitable way you want. 

It says in
Fataawa al-Lajnah al-Daa’imah: 

The basic principle is
that if whatever was vowed is something that is prescribed or allowed in
sharee’ah, then it should be spent in the manner intended by the one who
made the vow. If he did not make any specific intention then he may spend it
in any manner in which charity is given, such as giving to the poor and
needy…” 

Fataawa
Islamiyyah, 3/485. 

Giving to
your brother and your cousins who are in need is a kind of doing good, and
in fact giving to needy relatives is better than giving to others.
Al-Bukhaari (146) and Muslim (998) narrated that Anas ibn Maalik (may Allaah
be pleased with him) said: Abu Talhah was the richest of the Ansaar of
Madeenah in date-palms, and the most beloved of his wealth to him was
Bayruha’ (the name of a garden), which was opposite the mosque. The
Messenger of Allaah (peace and blessings of Allaah be upon him) used to
enter it and drink from its good water. When this verse was revealed
(interpretation of the meaning): 

“By no
means shall you attain Al-Birr (piety, righteousness — here it means
Allaah’s reward, i.e. Paradise), unless you spend (in Allaah’s Cause) of
that which you love”

[Aal
‘Imraan 3:92] 

Abu Talhah
went to the Messenger of Allaah (peace and blessings of Allaah be upon
him) and said: “O Messenger of Allaah, Allaah says, ‘By
no means shall you attain Al-Birr (piety, righteousness — here it means
Allaah’s reward, i.e. Paradise), unless you spend (in Allaah’s Cause) of
that which you love’, and the most beloved of my
wealth to me is Bayruha’; it is charity for the sake of Allaah and I hope
for its reward stored with Allaah. Give it, O Messenger of Allaah, as Allaah
guides you.” The Messenger of Allaah (peace and blessings of Allaah be
upon him) said: “Well done! That is a good deal! I heard what you said, and
I think that you should give it to your relatives.” Abu Talhah said: “I
shall do that, O Messenger of Allaah.” So Abu Talhah shared it out among his
relatives and the sons of his uncle. 

Charity
given to a relative is both charity and upholding the ties of kinship. See
questions no.
21810 and
20173. 

You do not
have to tell them that this is charity or the fulfillment of a vow. See
question no.
33777. 

But you
should not give it to one who will use it to help him disobey Allaah or who
is known for being extravagant or showing off, because Allaah says
(interpretation of the meaning): 

“Help you
one another in Al-Birr and At-Taqwa (virtue, righteousness and piety); but
do not help one another in sin and transgression”


[al-Maa’idah 5:2] 

You can find out what they need and buy it for them, instead of giving them the money. This will ensure that your charity is spent as it should be.