The imam stood up for the third rak'ah and forgot the first tashahhud, then remembered and went back. Is his prayer invalid?

Question:
He says: Honorable Shaykh, may Allah grant you success, the imam made a mistake in the Dhuhr prayer and did not sit for the first tashahhud, but rather stood up for the third rak'ah,

Answer:
Yes. The imam made a mistake in the Dhuhr prayer and did not sit for the first tashahhud, but rather stood up for the third rak'ah. When he heard the tasbih of two people, he went back and sat down, then completed his prayer and performed the prostration for forgetfulness. After the prayer, one of the ma'mum said that our prayer is invalid and must be repeated, because the imam went back from a pillar to an obligatory act. This is correct. No, it is not invalid. The imam is ignorant; this imam is ignorant, so he is excused for his ignorance. Also, they say that it is disliked to go back if he has started. It is disliked to go back. So if he has started the recitation, if he has started the Fatiha, it is forbidden to go back because he has started the pillar. So there is a difference between his standing before starting the recitation and starting the recitation. This is disliked and not forbidden. The prayer is valid in any case, if Allah wills, and he is excused for his ignorance. Yes.