Is it permissible to pay the deficient zakat from past years on behalf of a deceased person from the money of the endowment he bequeathed, or must it be paid in one lump sum from the inheritance money?

If the deceased had unpaid zakat (definition), the heirs must pay it from the estate before distributing the inheritance and executing bequests. This is because debts, whether owed to Allah or to people, take precedence over the rights of heirs and bequests. The scholars of the Permanent Committee for Issuing Fatwas were asked about a man who died owing zakat for several years, and they replied that it is obligatory to pay the zakat from his money for all the past years. If the man bequeathed a portion of his wealth as an endowment, his bequest is executed as long as it does not exceed one-third of the estate. In the case of debts owed by the deceased (such as zakat or other debts) and a bequest, the debts take precedence over the bequest and are paid from the estate first. Then, the bequest is executed from what remains. Al-Buhooti stated in "Al-Rawd Al-Murbi'": "Zakat, if the one upon whom it was obligatory dies, is like debt in the estate." Sheikh Muhammad bin Uthaymeen explained that the rights related to the estate are classified as follows: expenses for preparing the deceased for burial, then rights related to the specific asset of the estate (such as a mortgaged debt), then absolute debts (like zakat), then bequests of one-third or less to a non-heir, and finally, the inheritance. Based on this, it is not permissible to count the bequest as part of the zakat. Rather, the zakat is paid first from the total estate, then the bequest is executed within the limits of one-third, and anything exceeding one-third is not executed except with the consent of the heirs.