The Western notion of complete equality between men and women has so predominantly occupied the minds of many Muslims that they unfortunately started to doubt certain basics of their religion which they deem to be in contrast with this seemingly static belief. It is really a strange attitude from a Muslim to judge the principles of his or her religion by the scale of Western criteria.
Out of His unfathomable wisdom and all-encompassing knowledge Almighty Allah has set the regulations of inheritance and did not leave the matter to people’s different considerations, which are largely determined by narrow perspectives and/or whimsical passions. A Muslim by his very name has to profess total submission to the injunctions of his Lord even if he cannot discover the hidden wisdom of any of them. (Indeed Allah knows and you do not know) (Al-Baqarah 2: 216)
Shedding more light on this question, Dr. Monzer Kahf, a prominent economist, said the following:
1. The inheritance system, specifically the shares of daughters and boys, is mentioned in the Qur’an itself. As Muslims we have no choice but to accept them even if we sometimes do not understand the wisdom behind them.
2. We know with complete confidence that Allah is Just and Merciful and that He is the One Who has distributed these shares. So, there must be justice and mercy behind it.
3. Men give mahr (dower) in marriage, as it is obligatory and very substantial. Girls receive this mahr and are not required to spend it on the family or the husband. They save and invest it. Husbands are the ones who are fully responsible for all expenses of the wife and the children.
4. I know, as everybody else knows, that there are women who are much better in the eyes of their parents than men and they help them more than the boys, financially and otherwise. However, according to the sharia, the financial responsibility toward parents as well as all women in the family (such as sisters, aunts, etc.) falls first on the boys and only if they are not able then on others.
5. If some part of the sharia is not implemented in certain areas, this does not mean that we can be excused for not implementing the other parts, even when they appear, stand alone, as inconsistent with other practices that exist (and that are in deviation from the sharia).
For instance, if your daughter did not ask for a substantial mahr when she got married, this does not give you excuse to not implement the Islamic code of inheritance. Moreover, if she shares family expenses of her own or spend on her parents and the boy does not shoulder his responsibility, all that does not make a premise to violate the sharia in inheritance.
6. Finally, parents, while alive, can reward their good children materially and spiritually, but not by changing the inheritance system because it is mandatory as clearly mentioned in Verses 10 to 14 of surat Al-Nisa‘. Reward during a parent’s lifetime can be done by giving gifts to the good children and by supplicating Allah so that He may help them and be bountiful to them. Of course, we cannot tamper with the inheritance shares because when one of us dies, he or she is no longer an owner and the estate goes back to Allah Who gave us clear and detailed instructions about how to distribute the inheritance.