Praise be to Allah.
and blessings and peace be upon the Messenger of Allaah.
The female takes half the share of a male in inheritance regardless of whether she works and spends on the household or not, because this is the ruling of Allaah. Allaah says (interpretation of the meaning):
“Allaah commands you as regards your children’s (inheritance): to the male, a portion equal to that of two females”
This means that if a man and woman are co-heirs, then the male’s share is equal to that of two females. An exception is made when uterine brothers and sisters (related through the mother) inherit, in the case of kalaalah, which is mentioned in the passage (interpretation of the meaning):
“If the man or woman whose inheritance is in question has left neither ascendants nor descendants, but has left a brother or a sister, each one of the two gets a sixth; but if more than two, they share in a third”
The word kalaalah refers to a case where the deceased leaves behind no ascendants or descendents; if he has brothers and sisters through his mother (uterine siblings), then each male receives a share equal to that of one female. Al-Qurtubi (may Allaah have mercy on him) said: “There is consensus on this among the scholars; in the laws of inheritance there is no case where males and females receive equal shares except in the case of uterine siblings”.
Because of the importance of inheritance, Allaah explained the ruling on how the estate is to be divided Himself, and He did not leave the matter to human reasoning or interpretation. Hence Allaah concluded this aayah with the words (interpretation of the meaning):
“(these fixed shares) are ordained by Allaah. And Allaah is Ever All‑Knower, All‑Wise”
Allaah comments on the rulings of inheritance by saying (interpretation of the meaning):
“These are the limits (set by) Allaah (or ordainments as regards laws of inheritance), and whosoever obeys Allaah and His Messenger (Muhammad) will be admitted to Gardens under which rivers flow (in Paradise), to abide therein, and that will be the great success.
And whosoever disobeys Allaah and His Messenger (Muhammad), and transgresses His limits, He will cast him into the Fire, to abide therein; and he shall have a disgraceful torment”
From this it may be known that there is no room for changing or altering these rulings, or to suggest something different, because they came from Allaah, the All-Knowing, All-Wise, Who does not do the slightest injustice to mankind, and Who is more compassionate towards His slaves than a mother to her child.
Some scholars have sought to explain the reason behind giving males more than females in inheritance by referring to the verse (interpretation of the meaning):
“Men are the protectors and maintainers of women, because Allaah has made one of them to excel the other, and because they spend (to support them) from their means”
They said that because the man is obliged to spend on the woman, and on her children and servants, and she is spared that obligation, so it is appropriate that his share should be greater than hers.
This is one of the obvious reasons, no doubt. The great scholar al-Shanqeeti (may Allaah have mercy on him) said in Adwaa’ al-Bayaan: “because the one who in charge of another and spending money on him will always have his money decreasing, and the one who is being looked after and on whom the money is spent is expected to have more. The wisdom of giving precedence to the one on whose money more demands are made over the one whose money is expected to increase is to make up for the expenses of the former. This is sound reasoning.” (1/308).
It should be noted that Islam preceded all the customs and laws in honouring women and treating them fairly, and allowing them financial independence, whereas European women were, until recently, denied the authority to own anything!
With regard to what is mentioned in the question about a woman who spends on the household or contributes to the household expenses, the answer is that women are not required to do that, and they can refuse to work or refuse to spend their money that they have earned themselves, and ask their husband to spend on them and provide accommodation for them and their children. If the husband refuses to fulfil this right, then she may ask for a divorce. But if she agrees to spend on him and share the household expenses, then this is a good deed on her part for which she will be rewarded. But it is not obligatory for her to do that, and it has no effect on her share of inheritance.
It should also be pointed out that this wife may take half the estate of her father or mother, if she has no brothers, or she may inherit from her brother or sister, in addition to whatever she is entitled to from her husband’s estate after he dies.
And her husband may be in the opposite situation, I mean that he may inherit a small amount from the estate of his father, mother or brothers, or he may not inherit anything.
The point is that the words “to the male, a portion equal to that of two females” have to do with males and females among the children of the deceased; they do not apply to the husband and wife, as each of them have independent sources from which they may inherit.
And Allaah knows best.