Qadha prayers of parents is obligatory on the eldest son

1399. If a father did not offer some of his obligatory prayers or fasts, after his death, it is obligatory upon his eldest son, to perform its Qadha. If the son cannot do so, he may hire someone to perform them. Even if father was not able to give Qadha, moreover, as per precautionary measures, even if the father left it as a deliberate act of transgression, it is obligatory upon the son to give its Qadha or hire someone.