Firstly: 

Undoubtedly these kinds of family problems and annoyances are things that affect one’s life and occupy one’s thoughts, but with a little wisdom, proper conduct, more rational thinking, adhering to the path of fairness and patience for the sake of pleasing the one who has the greatest rights over you – namely your mother – and pleasing the one whom you love, the source of your comfort and the mother of your children – namely your wife – we can resolve the problem and handle the matter in the best manner possible. 

Secondly: 

We must – may Allah guide us and you aright – inform each party of the rights of the other. The mother must understand that her son’s wife has rights that have been ordained by Allah and taught by the Messenger of Allah; the wife must understand that the mother has rights ordained by Allah and affirmed by the Messenger of Allah. 

Moreover, each of them must understand that when Allah ordained rights for people, He forbade mistreatment and enmity, and He forbade transgressing the limits that He has set for His slaves. So what we must do is adhere to those limits and no one who has been given rights should transgress the limits in order to transgress against the rights of anyone else. 

Thirdly: 

We should explain the standard of fairness that has been outlined in Islam, which is that a person’s faith is not truly complete until he loves for his brother what he loves for himself, and until he hates for his brother what he hates for himself. 

So we ask the mother: would you accept for anyone – no matter who he is – to direct hurtful words towards you, or to mistreat you by behaving in an inappropriate manner, or to say bad things about your family, and so on? 

We ask the wife: would you be happy for my mother to be angry with me and not be pleased, and to pray against me instead of praying for me? Would you like that for yourself, no matter what the reasons? 

By presenting the case in such a manner, discussing it with two people you care for and who you do not want to make angry with you, you can persuade them, without putting the one who is in the wrong – especially your mother – on the spot and accusing her of transgression and hostility, or speaking ill of her and her actions, which may make matters more complicated and difficult to resolve. Rather you can achieve that with wisdom and choosing your words carefully. 

Then you should speak to your wife, encouraging her to pardon and overlook. 

Allah, may He be exalted, says (interpretation of the meaning):

“The good deed and the evil deed cannot be equal. Repel (the evil) with one which is better (i.e. Allah ordered the faithful believers to be patient at the time of anger, and to excuse those who treat them badly), then verily! he, between whom and you there was enmity, (will become) as though he was a close friend”

[Fussilat 41:34]. 

The Messenger of Allah (blessings and peace of Allah be upon him) said: “No one forgives, but Allah increases him in honour.” Narrated by Muslim, 2588. 

According to another hadeeth: “No one is wronged and bears it with patience but Allah will increase him in honour.” Narrated by at-Tirmidhi, 2325; classed as saheeh by al-Albani. 

Explain to her that forgiving is more beloved and more pleasing to Allah, and tell her: “You will only be forgiving the most beloved of people to me, namely my mother, and that will only increase you in dearness to me.” 

Fourthly: 

It is not permissible for your wife to cut off her relationship with your mother by shunning her and boycotting her, because it is not permissible for a Muslim to shun his brother for more than three days, as is well known. It is narrated in a saheeh report that the Prophet (blessings and peace of Allah be upon him) said: “Whoever forsakes his brother for a year, it is as if he shed his blood.” Narrated by Abu Dawood, 4915;classed as saheeh by al-Albani. 

He also said: “It is not permissible for a Muslim to shun another Muslim for more than three days, because they will be drifting away from the path of truth so long as they are shunning one another. Whichever of them is first to reach out to his brother, his doing so will be an expiation for him. If he greets him and he (the other one) does not respond, the angels will return his greeting and the shaytan will respond to the other one. If they both die in that state, neither of them will ever enter Paradise.”

Narrated by Ahmad, 15824; classed as saheeh by al-Albani in as-Saheehah, 1246 

But if mixing with one another will always lead to annoyance for the wife, and insults to her family, then this is something that it is not permissible for the mother to do, and it is not permissible for you to keep quiet about it, because people’s rights should be respected and if anyone harms a Muslim with no justification, the score will be settled on the Day of Resurrection. 

There is a well-known report about the bankrupt person who will come on the Day of Resurrection with prayer, fasting and zakah to his credit, but he will come having insulted this one, reviled that one, devoured the wealth of this one, shed the blood of that one and beaten another one. So each of them will be given some of his hasanat, and if his hasanat run out before what he owes has been paid off, some of their bad deeds will be taken and added to his burden, then he will be thrown into the Fire. 

So it is essential to alert your mother to this great danger and to advise her concerning that, in a gentle manner, and remind her to fear Allah. 

Based on that, if your mother persists in treating your wife in this manner, then the right thing to do is not to enable her to do that, by preventing your wife from going to see her, and there will be no blame on your wife in that case if she does not mix with her, visit her or go to see her. This is not obligatory upon her in the first place; rather what is obligatory is not to shun a person without any shar‘i justification that would make doing so permissible. 

If we assume that your wife overlooks and forgives her, and gives up her own rights, then what about the rights of her family? What have they done wrong to deserve this criticism and mistreatment without any error or sin on their part? 

But if it so happens that your wife and your mother meet in some place, then your wife has to greet her with salam if she meets her; the better of the two will be the one who is first to greet the other. If your mother speaks to her or greets her with salam, then she must return her greeting. 

In that case it will not matter if your mother threatens to pray against you and to be displeased with you, because Allah has forbidden injustice to Himself and has made it haram among people, and He has stated that He does not love those who are unjust or wrong others, as He, may He be exalted, says (interpretation of the meaning):

“O you who believe! Stand out firmly for Allah and be just witnesses and let not the enmity and hatred of others make you avoid justice. Be just: that is nearer to piety”

[al-Maidah 5:8]. 

What is meant is: stand out firmly for Allah and be just in word and deed, and be like that towards both relatives and strangers, friends and enemies. 

Do not let the hatred of some people cause you to treat them unfairly; rather, just as you would testify in favour of your friend, you should also testify against him (if need be), and just as you would testify against your enemy, you should also testify in his favour; even if he is a disbeliever or innovator, it is obligatory to treat him fairly. 

See: Tafseer as-Sa‘di, p. 224 

Moreover, just as it is not permissible to let hatred of some people make you fail to be fair, it is not permissible to let love of others make you fail to be fair; rather you should be fair in all cases.

 There is no blame on you for any of this, if you have tried to bring about reconciliation as much as you can, but were unable to achieve that. If your mother threatens to pray against you and so on, Allah, may He be exalted, will not answer the supplication of one who prays wrongfully or on the basis of severing ties of kinship. 

But it is essential that you take care to treat her properly and be patient in putting up with any unpleasantness on her part in all situations. 

And Allah is the Guide to the straight path. 

Please see also question no. 82453

Note: 

With regard to the words of the questioner: “I still offer supplication for her when I pray and I give in charity on her behalf”, offering supplication for her is a good deed and comes under the heading of honouring her and treating her kindly. But giving charity on her behalf when she is still alive is something that is not known from the early generations; rather what is known is giving charity on behalf of one who has passed away. Al-Bukhari (2760) and Muslim (1004) narrated from ‘Aishah (may Allah be pleased with her) that a man said to the Prophet (blessings and peace of Allah be upon him): My mother died suddenly and did not leave a will. I think that if she had been able to speak, she would have given charity. Can I give charity on her behalf? He said: “Yes, give charity on her behalf.” 

An-Nawawi said: 

This hadeeth indicates that giving charity on behalf of the deceased will benefit the deceased and the reward for it will reach him. There is scholarly consensus on this point. End quote. 

So what is prescribed is to focus on serving her, and praying for her in her absence, upholding ties with her by giving money and food, and so on, without giving charity on her behalf, because there is no evidence that doing so is prescribed (when she is still alive), as far as we know. 

And Allah knows best.