Kaffarah as obligatory for a sick person that should be made after recovery
Your father must offer
a Kaffarah (expiation) assigned for involuntary manslaughter. He has to free one believing slave. If there are none available, he must fast for two consecutive months and repent to Allah. If he is not able to fast, fasting will remain a duty that he must observe once he is able to. Similarly, if he missed some days in the past Ramadan, he has to fast them. It is not permissible for him to break his fasting due to his doubts and worries about the diseases he has. Only when a trustworthy Muslim doctor says that fasting entails harm, it will be permissible for him to break his fast and make up for these days later. If his disease is chronic, he has to pay Fidyah (ransom); feeding one Miskin (needy) for every day he breaks his fast in Ramadan. The Fidyah is one Sa` (1 Sa`=3 kg. Approx.) from the staple food in your area. As for the fasting of the Kaffarah (expiation), he should free one slave, if available, even out of his legacy after death. If it is not available and your father dies before observing the fasting, one of the heirs may fast on his behalf, this would be sufficient. The Prophet (peace be upon him) said,
If anyone dies in a state (that he had to complete) some days of fast, his heir must fast on his behalf.
(Agreed upon by Al-Bukhari and Muslim)
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.