Deviating from the order of surahs within a single rak'ah

The questioner:
Honorable Shaykh, may Allah grant you success. If the imam recites a surah and then does not know how to complete it, or forgets it, and then recites a surah after it in the same rak'ah, thereby deviating from the order in a single rak'ah, is the prayer invalid?

The Shaykh:
What is it?

The questioner:
If the imam recites a surah and then does not know how to complete it, or forgets it, and then recites a surah after it in the same rak'ah, thereby deviating from the order in a single rak'ah, is the prayer invalid?

The Shaykh:
So, as the applause indicated, one does not recite anything before it, and one does not recite anything before it in a single rak'ah. As for reciting after it, this is what the applause indicated: if he starts a surah and is unable to proceed in it, then he recites from the surah that follows it, starting from where he began, but he does not recite from the surah that precedes it. This is what the applause indicated.