What is the ruling on someone who recited the Tashahhud inadvertently in the third rak'ah and remembered while doing so? Should he stand up immediately? And what is the ruling on someone who recited the Tashahhud twice inadvertently, in the second and third rak'ahs? And what is the ruling on someone who completely forgot the Tashahhud and only remembered it after the Tasleem?

1. If a worshiper recites the Tashahhud in the third Rak'ah by mistake, then remembers, he should immediately stand up and perform the prostration of forgetfulness (Sujud al-Sahw), because an addition of the same type as the prayer invalidates it if done intentionally, and requires Sujud al-Sahw if done by mistake.

2. If a worshiper recites the Tashahhud in the second and third Rak'ah by mistake, he must perform the prostration of forgetfulness (Sujud al-Sahw) to compensate for the addition.

3. If a worshiper forgets the first Tashahhud and does not remember it until after the Taslim (salutation of peace), he must perform the prostration of forgetfulness (Sujud al-Sahw) if he remembers it soon thereafter; otherwise, it is waived.