Is it acceptable to stipulate a condition in the marriage contract that her husband should not inherit from her if she dies?
Question

                If a wealthy widow with children decides to remarry, can she put a clause in the marriage contract saying that after her death only her children will inherit from her and her new husband will give up any inheritance rights?
Praise be to Allah.
      The basic principle with regard to contracts and conditions 
      is that they are permissible and valid, and none of them are haraam or 
      invalid except that which is contrary to sharee‘ah. 

    Stipulating that the husband should be deprived of inheriting 
    in the event of the wife’s death is a condition that is contrary to 
    sharee‘ah, because it is cancelling out the right of the husband that Allah 
    granted him to a share of his wife’s wealth in the event of her death. 

    Al-Bukhaari and Muslim (1504) narrated from ‘Aa’ishah (may 
    Allah be pleased with her) that she said: The Messenger of Allah (blessings 
    and peace of Allah be upon him) said: “What is the matter with people who 
    stipulate conditions that are not in the Book of Allaah? There is no 
    condition that is not in the Book of Allaah but it is invalid, even if there 
    are one hundred conditions. The Book of Allaah is more deserving of being 
    followed and the conditions of Allaah are more binding.” 

    Al-Qurtubi (may Allah have mercy on him) said: 

    i.e., conditions that are not acceptable according to 
    sharee‘ah are invalid even if they are many. 

    End quote from Fath al-Baari, 5/189 

    Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) 
    said: 

    Whoever stipulates conditions in a waqf, manumission, a gift, 
    a sale, a marriage contract, rental, vow and so on that is contrary to what 
    Allah has decreed for His slaves in that those conditions enjoin something 
    that Allah has forbidden or forbid something that Allah has enjoined, or 
    they permit something that He has prohibited or prohibit something that He 
    has permitted, then these conditions are invalid according to the consensus 
    of the Muslims of all eras. 

    End quote from Majmoo‘ al-Fataawa, 31/28 

    He also said: 

    If a condition is contrary to the conditions of Allah and His 
    Messenger, it is invalid, such as if he stipulates that his son or his 
    relatives should not inherit from him, or that he should help him in 
    everything he wants and support him against everyone who opposes him whether 
    he is in the right or otherwise, or that he should obey him in everything he 
    tells him to do, and other such conditions. 

    And when such conditions are made, then one should fulfil the 
    part of it (the contract) that is in accordance with the commands of Allah 
    and His Messenger (blessings and peace of Allah be upon him), and he should 
    not fulfil the part that is contrary to that. This is agreed upon among the 
    Muslims. 

    End quote from Majmoo‘ al-Fataawa, 35/97 

    And Allah knows best.