regarding the ruling on establishing a second congregation in the mosque?

The questioner : There is a mosque with many regular worshippers, meaning people from the area, and the number of worshippers varies. So, at the time of prayer, after the iqamah, the regular imam was delayed... so they established the prayer, and one of them led them. The people of the mosque—meaning the people of the area—waited for the imam, the regular imam. They said: "Do not pray." When the regular imam arrived, the prayer was established a second time, and they prayed as two congregations in the mosque at the same time; meaning, perhaps they were behind by one or two rak'ahs?

The Shaykh : The answer is that the first congregational prayer is valid; it is not said to be invalid, but it is a sinful congregation in another respect; because they started without permission and encroached upon the right of the imam. However, the imam, in turn, made a mistake when he should have been patient until this congregation dispersed, bearing their sins, and then he would have performed his prescribed congregation. As for striking back at the first congregation on the grounds that they are encroaching, he is encroaching upon them while they are an established congregation. This is permissible according to the school of Abu Nuwas, who said:
"Cure me with what was the disease."

The questioner : ...On the same topic, was it better for the shaykh to lead the first congregation or to wait?

The Shaykh : No, because this congregation is encroaching; so he should not lead them.