In The Name of Allaah, The Most Merciful, The Bestower of Mercy.
Question: Does a person become sinful due to failing to fulfil deeds of obedience [to Allaah]? And what is obligated on a person if he misses an act of worship which he is determined to perform, even though he was prevented from performing it due to illness or a legislated shariah excuse?
Answer: If a Muslim always performs a deed of obedience to Allaah when he is at home, but then he is prevented from performing it due to a legislated excuse, he will be rewarded even if he did not perform it. Abu Moosaa [radiyallaahu-anhu] reported that the Messenger [sallal laahu alayhi wasallam] said, “If a slave of [Allah] becomes sick or travels, he is rewarded for the good deeds he used to perform when he was healthy or at home.
As for the deeds he abandons whilst having the ability to perform them, he will be deprived of their reward. And this may lead to sin [i.e. if obligations are abandoned]. Therefore, it is incumbent upon a person that he repents to Allaah, seeks Allaah’s forgiveness often and be eager to perform deeds of obedience to Allaah, so that Allaah may aid him. [Source: Fadaa’il Al’A’maal page 8’ by Shaikh Muhammad Bin Abdillaah As-Subayyil (rahimahullaah)]