Can an unbeliever make a bequest to a Muslim and vice-versa, with regard to an inheritance, and what are the impediments to a bequest?

A Muslim's bequest to a non-Muslim is valid within the limits of one-third, just as a non-Muslim's bequest to a Muslim is valid. The division of inheritance follows Allah's division of inheritances in the Qur'an and Sunnah (definition); a Muslim does not inherit from a non-Muslim, nor vice versa. Impediments to a bequest include anything forbidden by Islamic law, a bequest to an heir, or a bequest of more than one-third unless the heirs agree, based on the Prophet's (peace and blessings be upon him) saying: "A third, and a third is much," and "There is no bequest for an heir unless the heirs wish it."