Sahw: forgetting a binding duty or adding an unwarranted prayer act; sujud al-sahw can compensate.
Doubt: uncertainty about rakah count; repeated uncertainty is resolved by stronger judgment or certainty.
Invalidity: missing an essential pillar or adding an act that destroys the fard prayer’s status; two compensatory prostrations cannot repair that by themselves.
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Prostrations of Forgetfulness: Causes, Method, Missed Sittings and Doubts
Sahw: forgetting a binding duty or adding an unwarranted prayer act; sujud al-sahw can compensate.
Doubt: uncertainty about rakah count; repeated uncertainty is resolved by stronger judgment or certainty.
Invalidity: missing an essential pillar or adding an act that destroys the fard prayer’s status; two compensatory prostrations cannot repair that by themselves.