In principle, we should understand that Allah Ta’ala’s mercy knows no
limits. Allah Ta’ala rewards a person on the basis of the most insignificant
and minutest of actions. This is solely based on one’s intentions. A person
who merely intends at heart to do good is rewarded fully on the basis of his
intention even though he was unable to do the action.
Similarly, here in your case, you have enough wealth to spend in charity so
you will be rewarded if you spend. If your wife does not have wealth to
spend in charity but she makes this intention at heart that if she had
wealth, she would have spent it in charity, then she is also being rewarded
fully by Allah Ta’ala on the basis of her pure intentions.
Nevertheless, in all cases the wife earns tremendous amount of reward even
though she does not physically prepares for her husband, the dishes that she
washes and all the other chores is in reality charity and will earn lots of
reward for her.
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai