He gave his mother a gift then she bequeathed it to him after her death
Question

                I have bought a gift of great value for my mother before she passed away. She said to everyone that the gift should be returned to who bought it for her after I die. Is it considered of her heritage, do I have to ask my brothers’ permission to take it, knowing that they do not mind? What makes me confused is what the prophet (PBUH) said: “There is no will for the heirs” in case we consider my gift included in the heritage.
Praise be to Allah.
    What you gave to your mother and she accepted from you has 
    become her property, and the basic principle is that it is part of her 
    estate which is to be divided among all of her heirs. But her saying that 
    gifts are to be returned to the one who gave them after she died, which is 
    clearly a bequest in your favour, is a bequest to an heir as you say. Abu 
    Dawood (2870), al-Tirmidhi (2120), al-Nasaa’i (4641) and Ibn Majaah (2713) 
    narrated that Abu Umaamah said: I heard the Messenger of Allaah  (peace 
    and blessings of Allaah be upon him) say: “Allaah has given each person who 
    has rights his rights, and there is no bequest for an heir.” Classed as 
    saheeh by al-Albaani in Saheeh Abi Dawood. 

    This bequest should not be executed unless the heirs agree, 
    so long as they are adults of sound mind. As for one who is not an adult of 
    sound mind, such as a minor, his agreement does not count, and it is not 
    permissible to detract anything from his share in the interests of the one 
    for whom the bequest was made. 

    It says in one of the versions of the hadeeth quoted above 
    from Ibn ‘Abbaas (may Allaah be pleased with him): “It is not permissible to 
    make a bequest to an heir unless the other heirs agree.” Narrated by 
    al-Daaraqutni and classed as hasan by al-Haafiz Ibn Hajar in Buloogh 
    al-Maraam. 

    Ibn Qudaamah (may Allaah have mercy on him) said in 
    al-Mughni (6/58): “There is no bequest for an heir, unless the other 
    heirs allow that.” To sum up, if a person makes a bequest to one of his 
    heirs and the other heirs do not agree to it, then it is not valid, and 
    there is no difference of opinion among the scholars concerning that. Ibn 
    al-Mundhir and Ibn ‘Abd al-Barr said: The scholars are unanimously agreed on 
    that, and there are reports from the Messenger of Allaah  (peace and 
    blessings of Allaah be upon him) to that effect. Abu Umaamah narrated: I 
    heard the Messenger of Allaah  (peace and blessings of Allaah be upon 
    him):  “Allaah has given each person who has rights his rights, and there is 
    no bequest for an heir.” Narrated by Abu Dawood, Ibn Majaah and al-Tirmidhi. 
    … But if they agree to it then it is permissible, according to the majority 
    of scholars. End quote.  

    It says in Fataawa al-Lajnah al-Daa’imah (16/317): It 
    is not permissible to bequeath more than one-third, and it is not valid to 
    make a bequest to an heir, unless the heirs who are adults of sound mind 
    give up part of their shares, because the Prophet  (peace and blessings 
    of Allaah be upon him) said: “Allaah has given each person who has rights 
    his rights, and there is no bequest for an heir.” Narrated by Ahmad, Abu 
    Dawood, al-Tirmidhi and Ibn Majaah, and by al-Daaraqutni who added at the 
    end: “unless the other heirs agree.” End quote. 

    And Allaah knows best.