Is it permissible for a childless couple to donate all their wealth as charity for good causes after their death, knowing that each has their own private funds, and due to the heirs having no need and out of a desire to avoid their greed and their failure to give charity on their behalf?

If the owner of wealth has an heir, it is not permissible for him to bequeath all of his wealth, due to the hadith (definition): "Indeed, Allah has given every rightful person his due, so there is no bequest for an heir," and because the wealth automatically transfers to the heirs upon death.

If the testator violates this and bequeaths all of his wealth, the bequest is not executed except within the limit of one-third. Anything exceeding one-third depends on the approval of the heirs. As for sustenance, charity, and gifts during one's lifetime, the owner of wealth may give as much as he wishes from them.