What is the ruling on one who forgets to recite al-Fatihah

Question:
What is required of one who doubts during the recitation of a surah that he did not recite al-Fatihah, so he recites al-Fatihah and then repeats the surah more than once?

Answer:
Answer: If he doubts about reciting al-Fatihah, if this is a matter of waswas (whispers), he should leave it alone. As for if it is not a matter of waswas, he should recite al-Fatihah so that his conscience is clear regarding this pillar of certainty. As for repeating the surahs or reciting the surahs again, this is not required, because what comes after al-Fatihah is a recommended practice (sunnah), whereas al-Fatihah is a pillar of the prayer. However, al-Fatihah is not repeated, and a pillar is not repeated except in the case of doubt during the prayer. As for doubt after completing the act of worship, it has no effect and is not to be heeded.