The ruling on the ma'mum following the imam if he sits for the first tashahhud after the third rak'ah

Question:
The imam prayed 'Asr and stood up for the third rak'ah before sitting for the first tashahhud. The congregation alerted him, but he did not go back. Then he sat for the first tashahhud in the third rak'ah, and the congregation alerted him, but he did not stand up. Then he stood up and sat for the final tashahhud in the fourth rak'ah. What is obligatory for us? And does the ma'mum follow the imam if the ma'mum is certain that he is in error?

Answer:
If he stood up for the third rak'ah and did not sit, and you recited the tasbih with him and he did not go back, you stand up. You stand up and follow the imam. The first tashahhud is dropped due to forgetfulness; it is made up with the two prostrations of sujud al-sahw. He does not sit in the third rak'ah if he realizes that he did not sit in the second. It is not permissible for him to sit in the second [meaning the third] because this is an addition to the prayer that is not in its proper place. So he does not sit. This is a matter of ignorance. As long as he is ignorant, the prayer is valid, if Allah wills. But he should be alerted to this. He should be alerted that if he relied on standing and did not sit for the first tashahhud, he should continue and perform sujud al-sahw before the taslim. He performs sujud al-sahw before the taslim, and this is sufficient, praise be to Allah.