As an illustration, a Muslim man has a Christian or a Jewish woman as a wife, and his parents are non-Muslims. Certainly, all these people are not his automatic inheritors (due to the difference in faith) – without any difference of opinion among the scholars on this point. Is it then proper for this Muslim to make a will to these relative and similar others who are not Muslims?
The scholars are unanimous that a will to a non-Muslim is proper – without any known different opinion.
In my opinion, consensus on that is proper if only the non-Muslim (kafir) is not a combatant. If he is a combatant, the Hanafi School of Thought is of the view that it is not proper, because of this verse: “it is only as regards those who fought against you on account of religion, and have driven you out of your homes, and helped to drive you out, that Allah forbids you to befriend them. And whoever will befriend them, then such are the zalimun (wrong-doers and those who disobey Allah). They say the verse explicitly forbids doing an act of righteousness to those who wage war against us and making a will is an act of good deed. This is the view of Asbagh of the Malik School of Thought.
I therefore hold that if it is established that any non-Muslim fights against Muslims and declares enmity on them or helps anyone who fights against any Muslim among us, it therefore becomes prohibited (haram) to make a will to him. This is because making a will to him (in this case) implies strengthening him and aiding his group to fight against the Muslims. Meanwhile, we have been ordered to fight such a kafir and take his wealth. How then would it be proper to make him benefit from the wealth of the Muslim?!
But the fact that Umar (RA) sent a dress to his polytheist brother in Makkah and he was of the “people of war”, definitely, clothing a naked brother is not regarded as helping the combatant kafir. It is only a gift, and (giving) a gift to a kafir combatant is allowed by consensus.
In summary, making a will of a lot of wealth which strengthens the kafir combatant and serves as a support for him against the Muslims is not allowed. Al-Bayhaqi and Abdurrazaq As-San’āni narrated that Safiyya (wife of the Prophet) willed one-third of her wealth to her Jewish brother. But regarding the kafir that makes a will to a Muslim, it is allowed by the majority of scholars, though the Shafi’i school of thought has two views.
On this ground, if a kafir makes a will to his Muslim son, he (i.e. the son) has every freedom to take the will on the condition that the will does not imply disobedience to Allah or any forbidden act.
In Sharh as-Siyar al-Kabir, it is mentioned that “if a (non-Muslim) martial (or fighter) in a war zone (or enemy territory), makes a will for all his wealth to go to a Muslim because (or as a guarantee) of assurance of his protection, he (the Muslim beneficiary) has the freedom to prevent all the heirs from it if it is possible”. Among the rules applicable to the people of war, (i.e. the enemy zone) is that the one to whom something is willed is more entitled to the will, and if such is not given to him, then one third should be given after settling his debt.
Here, it is worthy of mention that it is proper to will a dog which its acquisition is allowed like the one used for hunting or cultivating because in such is a legitimate benefit and the hand can settle on it (i.e. it is a tangible possession). And because it is also proper to offer it as a gift, it is therefore permissible and proper to make it a part of the will to others, just like other forms of wealth.