The will of a non-Muslim for his Muslim son
28-6-2011 | IslamWeb
Question:
Dear sheikhs, I understand that it is allowed for a Muslim to accept the will of a kafir parent and his or her share decided on in the will. However, the will of my non-Muslim father includes that half of his property should go to the church and the other half to me and my sister. Is it allowed for me to agree with this will that gives money to the church? Also, is it allowed for me to officially appoint a non-Muslim from the family to sign papers instead of me (since I'm in another country)? A quick reply would be highly appreciated since I have to decide what to do very soon... JazakAllahu khair
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad 
is His slave and Messenger.
First of all, it should be mentioned that it is not permissible for a will to exceed one-third of the inheritance, and if it exceeds one-third, then it can only be valid if all the heirs agree to it.
In your case, the will is made in the entire wealth, and the ruling about it will be detailed as follows:
Your father’s willing half of his wealth for the church is a void will according to the view that we adopt here in Islamweb because it is a will for what is forbidden. A will for what is forbidden is void whether it is made by a Muslim or by a non-Muslim; Ibn Qudaamah 
said: “Making a will for a sinful matter or what is forbidden is not valid whether the person who made the will is a Muslim or a Thimmi (i.e. a non-Muslim living under the Muslim rule). For example, if he makes a will for building a church or a Zoroastrian temple, or makes a will for maintaining them or spending on them, then it is a void will, and this is the view of Ash-Shaafi’i .”
Therefore, you are not permitted to accept the fulfillment of the will that your father had made for the church, and you must prevent that if you can do so.
As regards your father’s will for you and your sister, then if your sister is a Christian, then she is among the heirs and the will for her is also void (because she is an heir). In which case, what is valid from this will is only one-fourth.
Therefore, it is permissible for you to take what your father had willed for you because the will of a non-Muslim for a Muslim is valid. Ibn Qudaamah said: “As regards the will of a non-Muslim for a Muslim, it is valid unless his inheritance is alcohol [all kinds of intoxicants] or pigs.”
Moreover, Al-Mardaawi said: “Hence, the will made by a non-Muslim [for a Muslim] is absolutely valid.”
Besides, what your father had willed for you according to this estimation is less than one-third so it is permissible for you to take it and you do not need the consent of the other heirs.
On the other hand, in case your sister is a Muslim, and your non-Muslim father had given both of you half of his property as a will, then it is only one-third of the property that is a valid will which you are permitted to take. But you should not take whatever exceeds one-third except with the consent of the heirs of your father who are on the same religion like him, so if they agree to his will, it becomes effective. Ibn Qudaamah said: “In case a non-Muslim makes a will for his heir or a non-heir with more than one-third, then it depends on the consent of all other heirs, exactly like in the case of a Muslim….”
Allaah Knows best.