Wa `alaykum as-salamu wa rahmatullahi wa barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Dear questioner, we would like to thank you for the great confidence you place in us, we implore Allah Almighty to help us serve His cause and render our work for His sake.
It should be clear that the relationship between a woman and her in-laws and a man and his in-laws is based on mutuality and general rules of kindness.
Although a Muslim man is required to be kind and courteous to his parents, his parents cannot legally (according to the Shari`ah) dispose of the property, including salaries, of their adult children without their permission.
In his response to your question, Prof. Dr. Monzer Kahf, a prominent economist and counselor, states the following:
Dear sister in Islam, I like to be straightforward with you because I think that unless we are very clear on these issues, we will not be able to solve many of the social problems in our society and communities. Our failure to do this will give room for secularists and other people who do not carry Islamic values to take the driver’s seat in attempting to bring in solutions that contradict our culture and values. The following points are the principles that govern matters concerning your question according to the Shari`ah:
1- A husband is required to spend on his wife in accordance with his level of income and wealth. This is confirmed in the Qur’an and the Sunnah. This obligation is by virtue of the marriage contract and is required whether the wife is rich or poor or has income of her own or not. A married woman is not required to spend on herself from her own money.
2- A wife may take from her husband’s properties (wealth, income, salary, and other assets) even if she does not have his explicit permission in order to pay for what is needed for normal personal and family expenses. This includes giving sadaqat(charity) that people give to the poor and needy when an occasion arises. This is confirmed by at least two hadiths of the Prophet (peace and blessings be upon him) that state that a wife is the manager of her husband’s house and property, and she is responsible for her actions and the Hadith of Hind the wife of Abu Sufian [in which she asked the Prophet (peace and blessings be upon him) permission to take of her husband’s money to spend on the household without his knowledge and the Prophet (peace and blessings be upon him) allowed her to take what fairly meets the family necessary needs].
3- Parents have the right of service and spending on their children, married or single, if they need. Kindness to parents is required whether parents are in need or not. This means that children are required to spend on their mother and father only if they are in need, but if they are not in need, children are also required to be kind and courteous to their parents, both financially and socially. But parents cannot legally (according to the Shari`ah) dispose of the property, including salaries, of their adult children without their permission. A parent who lives with his or her child, and receives money from his or child may give to charity according to their circumstances.
4- The properties of husband and wife should not legally be mingled together. This means that each spouse is financially independent from the other. A husband has no right to dispose of the property of his wife, and she can do whatever she likes with her own property (including gifts given by the husband) on her own, she has no need to ask for permission from her husband, he does not even need have knowledge of this. In addition, neither his mother nor father or her husband has the right to interfere in this.
While a married man or woman is required to help and serve his or her parents, the relationship between a woman and her in-laws and a man and his in-laws is based on mutuality and general rules of kindness. A wife is not required to obey her mother-in-law nor serve her, and a man is not required to obey or serve his mother-in-law. There is nothing in our Shari`ah that puts an obligation on married women toward her in-laws except the general rules of mutuality, kindness, courtesy, and respecting elders.
Allah Almighty knows best.