Ruling when doubting whether the intention was for an obligatory prayer (fard) or a supererogatory prayer (nafl)?
Chapter on the Description of Prayer
Al-Mughni
Book of Prayer
Primary text
If doubt arises as to whether the intention was for an obligatory prayer or a supererogatory one, the prayer is completed as a supererogatory prayer. This ruling applies unless the person remembers having intended the obligatory prayer before performing any subsequent action.
Supporting text
If the recollection of having intended the obligatory prayer occurs after commencing another action (after the doubt), the two established views concerning invalidation upon performing an action while doubting the initial intention apply.