How should one advise a person who is praying a sunnah while the imam is praying?
Machine translationRead the Arabic original
Question:
If one finds a person praying the sunnah of the prayer while the imam is praying?
Answer:
He should be taught and warned that this is not permissible. He should be taught that this is not permissible. Some scholars hold that one may pray the rawatib, as the Hanafis do, but this is an error and a weak opinion.
Q: What about Fajr? May Allah reward you.
The Shaykh: Yes, neither Fajr nor any other prayer.
Q: But does he commit a sin?
The Shaykh: The one who knows commits a sin. The one who does not know may be excused due to ignorance, but if he knows, he commits a sin.
Q: Is his prayer invalid?
The Shaykh: Yes, it is invalid.
If one finds a person praying the sunnah of the prayer while the imam is praying?
Answer:
He should be taught and warned that this is not permissible. He should be taught that this is not permissible. Some scholars hold that one may pray the rawatib, as the Hanafis do, but this is an error and a weak opinion.
Q: What about Fajr? May Allah reward you.
The Shaykh: Yes, neither Fajr nor any other prayer.
Q: But does he commit a sin?
The Shaykh: The one who knows commits a sin. The one who does not know may be excused due to ignorance, but if he knows, he commits a sin.
Q: Is his prayer invalid?
The Shaykh: Yes, it is invalid.
Source
binbaz.org.sa
The Arabic text is copied verbatim from the original source, without any edits.