Is it considered an injustice to the eldest sister to deprive her of inheritance on the grounds that she had previously received her share, and is it considered an injustice to unmarried sisters to give them only what suffices for their marriage, with their consent, while the father agrees to sell the remainder of his property to the only son?

It is impermissible for a father to favor one of his children over others, except for a legitimate Shar'i reason, such as poverty. He must treat them justly, for the Prophet, peace and blessings be upon him, said: "Be mindful of Allah and treat your children justly." It is not permissible for the sons to resort to deception to deprive their sister of their father's inheritance or to seize his money through fictitious schemes, for the father's money is his property as long as he is alive. This involves deceit and trickery, regarding which it was said: "Whoever deceives us is not of us," and "Trickery and deception lead to Hellfire." The agreement of the two sisters to waive their right is not permissible because it is a waiver of a right that has not yet been established for them. The questioner should fear Allah and seek lawful sustenance through legitimate means, for Allah Almighty is the Provider. The Prophet, peace and blessings be upon him, said: "Indeed, the Holy Spirit inspired in my heart that no soul will die until it has fulfilled its sustenance and its term, so fear Allah and be gracious in seeking it."