—counted from the day he was born.
If, however, the prevailing presumption is that he has perished—such as one who disappears while still among his family (1) or in a deadly desert—the waiting period is four full years from the time he went missing; thereafter his estate is apportioned in both cases.

Section
Victims of Collapse and Drowning
If two people who may inherit from one another—such as two paternal brothers—die together beneath falling rubble, by drowning, or the like, and the order of their deaths cannot be ascertained and no dispute arises concerning it, each is deemed to inherit from the other’s original estate, but not from what the other had just inherited from him. Should there be disagreement over who died first, neither inherits from the other at all.

Section
Inheritance When Religions Differ
No inheritance passes between persons of different religions, except through the bond of walāʾ (patronage). A non-Muslim who embraces Islam before the division of his Muslim relative’s estate may inherit.

A belligerent non-Muslim, a dhimmī, and a mustaʾman may inherit from one another if they share the same religion; being of assorted faiths, they do not inherit when their religions differ.

An apostate neither inherits nor transmits inheritance; his property reverts to the public treasury (fayʾ).

A Magian (Zoroastrian) or the like may inherit once he becomes Muslim, or if he brings his claim of kinship before a Muslim court. The same ruling applies where a Muslim, under a mistaken presumption of permissibility, has intercourse with a woman who is one of his maḥrams; inheritance is not established through a marriage that would remain invalid even after his conversion to Islam.