My question is as follows: If a husband doesn’t provide for his wife, meaning, if he doesn’t maintain her, by not working and not earning any money, because of laziness, does she have in return the right to sexually refuse him?
Since the main obligation of a husband is to maintain his wife, which is in return for her sexual enjoyment, and since, if a wife refuses him sexually to spend the night with her, she forfeits her right of maintenance, doesn’t the reverse case come into effect then as well, when the husband refuses to maintain her?

I know that the wife has the right to ask for a divorce, if the husband doesn’t maintain her. But instead of going this final step, wouldn’t it be better and less grave to first refuse him sexually, before asking for a divorce? So that the husband has a chance to change, before he gets divorced?

Praise
be to Allah

The husband is obliged to spend on his wife’s maintenance, on
a reasonable basis, because Allah, may He be exalted, says (interpretation
of the meaning): 


“Men are the
protectors and maintainers of women, because Allah has made one of them to
excel the other, and because they spend (to support them) from their means”


[an-Nisa; 4:34]


“Let the rich
man spend according to his means, and the man whose resources are
restricted, let him spend according to what Allah has given him. Allah puts
no burden on any person beyond what He has given him”


[at-Talaq 65:7]. 

It was narrated that Mu‘awiyah al-Qushayri (may Allah be
pleased with him) said: I said: O Messenger of Allah, what are the rights of
the wife of one of us over him? He said: “That you feed her as you feed
yourself, clothe her as you clothe yourself, do not strike the face, do not
disgrace her and if you want to shun her (by way of disciplining her) do not
leave home.” 

Narrated by Abu Dawood (2142) and Ibn Majah (1850); classed
as saheeh by al-Albani in Saheeh Abi Dawood. 

This has been discussed previously in fatwa no.
145722 

If the husband fails to spend on his wife’s maintenance, then
she has the choice of leaving him or putting up with him. 

If she chooses to put up with him, in the hope that he will
change, if he is withholding her maintenance out of miserliness and
stinginess, or until his financial situation improves, if he is not well
off, then she is not obliged to allow him to be intimate with her. 

Ash-Shirazi ash-Shaafi‘i said in al-Muhadhdhab fi Fiqh
al-Imam ash-Shaafi‘i (3/155):

If she chooses to stay after he becomes unable to spend on
her, she is not obliged to allow him to be intimate with her, and she may
leave his house, because allowing intimacy is in return for maintenance, so
it is not obligatory when there is no maintenance. End quote.

Muhammad Najeeb al-Mutee‘i said in his Sharh
(20/169): 

If it is proven that the husband is no longer able to spend
on her, she has the choice of three options: she may annul the marriage; she
may stay with him and allow him to be intimate with her, and it is her right
that she should spend on her whatever he is able to spend; or she may remain
married to him, without having to allow him to be intimate with her – rather
she may leave his house, because allowing intimacy is only obligatory upon
her when he spends on her maintenance, but he is not doing so in this case,
but she is not entitled to maintenance when she is keeping herself away from
him, because maintenance is only enjoined in return for allowing intimacy,
but in this case she is not allowing him to be intimate with her. End
quote. 

Al-Bahooti (may Allah have mercy on him) said in Kashshaf
al-Qina‘ (5/477): 

She has the right to remain in the marriage and not allow him
to be intimate with her, so she does not have to allow intimacy or reside in
his house, and he must not detain her; rather he should let her earn money,
even if she is well off, because he has not given her anything in return for
intimacy with her. End quote. 

However we should draw the wife’s attention to the fact that
refusing intimacy with the aim of making him mend his ways, correcting his
behaviour and the like is a means of amending and correcting someone’s
behaviour in which attention should be paid to the husband’s condition and
character, and the negative outcomes that may result from that, as well as
the hoped-for benefits. It may make some husbands escalate the quarrel and
become stubborn and get angry with his wife if she does such a thing, and he
would forget his own shortcomings and the wife’s aim of reforming him, to
the point that he ends up destroying the marriage. 

So be very careful, lest you make matters worse between
yourself and your husband when you are trying to put things right. Look
carefully at your husband’s situation and what you think will have a
positive impact on him; if you have a right over him, be wise and prudent in
exercising your rights. 

And Allah knows best.