What is the ruling on the followers praying behind an imam who prays tarawih before 'Isha, intending their prayer behind him to be the obligatory 'Isha prayer?

The questioner : It appears he prays tarawih with the people.

The Shaykh : How?

The questioner : He used to pray tarawih with the people based on his opinion and belief that it was tarawih, and the people believed he was praying 'Isha.

The Shaykh: All right.

The questioner : So they prayed 'Isha behind him, while he was praying tarawih, four rak'ahs, and he prayed with them.

The Shaykh : Yes.

The questioner : When he finished, he asked the people, and they said, meaning, the 'Isha prayer has ended. He saw from the actual situation that it was the 'Isha prayer, so he repeated his prayer alone by himself.

The Shaykh : Why?

The questioner : Because he intended, meaning, that he was praying the voluntary prayer, not the obligatory one. I say he prayed the obligatory prayer; he prayed the 'Isha prayer.

The Shaykh : He had prayed the obligatory prayer.

The questioner : He did not pray before that; he did not pray the obligatory prayer. He prayed with them directly, intending tarawih.

The Shaykh : Do you mean he prayed tarawih before the obligatory prayer?

The questioner : Before the obligatory prayer, yes.

The Shaykh : Yes, what he did is correct.

The questioner : Yes, he repeats it for himself alone.

The Shaykh : Yes.

The questioner : Yes, I told him that. I said the best is silence. Speaking causes fitnah (trial, discord or temptation). If I told them, it might cause him problems, meaning.

The Shaykh: Peace be upon you.