بسم الله الرحمن الرحيم
(Fatwa: 311/311/M=04/1437)
If your father had made a will to pay the fidyah (expiation) of his missed salah then it is wajib to pay it from third portion of his inheritance; otherwise it is not necessary on his heirs. Yes, if the heirs pay it from their own side then it shall be their favour and it is hoped that it shall suffice on behalf of their father and he shall not be questioned about it. The fidyah of one salah is equal to one Sadaqah al-Fitr either food or its price. The quantity of Sadaqah al-Fitr is half sa’ wheat which at present is equal to 1 kg and 574 gram and 640 milligram (1.575 kg). Witr is also a separate salah and one Sadaqah al-Fitr should be paid for witr salah as well.
Allah knows Best!
Darul Ifta,
Darul Uloom Deoband