What is the ruling on repeating a prayer whose validity was doubted, and then its invalidity became apparent?

Doubt concerning an act of worship after its completion does not affect its validity. If one doubts the invalidity of their prayer after finishing it, it remains valid until its invalidity becomes clear. If someone repeats a prayer with the intention of it being obligatory due to doubt about its validity, and then the invalidity of the doubted prayer becomes apparent, the repeated prayer suffices. Similarly, it suffices for someone who repeated a prayer to attain the virtue of congregational prayer, and then the invalidity of the first prayer became apparent, provided they had intended the obligatory prayer or submission to Allah in making whichever of them their obligatory prayer. One should be wary of obsessive whispers (waswas) due to their significant harm.