The ruling on one who stands with the imam for a fifth rak'ah due to doubt or ignorance

Question:
The imam stands up for a fifth rak'ah in a four-rak'ah prayer, and among the followers, some are in doubt and some are certain, so they all stand up with him?

Answer:
The one who is in doubt stands up, and the one who is certain says: Subhan Allah, Subhan Allah, to alert him, and does not stand up.
Q: And does the one who did it intentionally have to repeat the prayer?
A: No, he owes nothing as long as he is ignorant; he owes nothing as long as he is ignorant of the ruling of the Shari'ah.