Muharamat - Prohibitions That Are Taken Too Lightly. Islamic book

Writing a will for the purpose of harming one of the heirs

One of the basic principles of Sharee'ah is that there should be neither harming nor reciprocating harm. One example of this harm is writing a will that deprives one or some of the legitimate heirs of his or their rights. Such a person is warned by the Prophet (peace and blessings of Allaah be upon him): "Whoever harms (others), Allaah will harm him, and whoever makes things difficult for others, Allaah will make things difficult for him." (Reported by Imaam Ahmad, 3/453; see also Saheeh al-Jaami', 6348). Ways in which a person's will can harm others is by denying an heir of his rights, or giving an heir more than he is entitled to in Sharee'ah, or by bequeathing more than a third to any one person.

In places where people are not subject to the rule of Sharee'ah, it may be difficult for a person to take what is his by rights granted by Allaah, because courts that apply man-made laws may order that the unfair will registered with a lawyer be executed. "Woe to them for what their hands have written and woe to them for that they earn thereby." [al-Baqarah 2:79]