Led the people in Maghrib (Sunset)

Q 2: We performed the `Asr (Afternoon) Prayer behind the Imam (the one who leads congregational Prayer) of the Masjid (mosque), who stood up for a fifth Rak`ah (unit of Prayer); we said "Subahan Allah (Glory be to Allah)" out loud, but he did not respond. Therefore, some of the followers followed him while others sat down until the Imam sat down and said the Taslim (salutation of peace ending the Prayer), and then they said it after him. When the Imam and those who followed him were asked about that, he replied that he moved from an obligation [i.e. the sitting position] to an integral part of prayer [the standing] (i.e. this means he cannot retract his action again) and he mentioned some Hadith to us [in support] such as the Hadith related by Ibn Mas`ud and the commentaries of the scholars on it. My question is: Is our prayer correct or not? Is what he and his supporters said true? Is the action of those who were praying correct? Please give us your opinion, may Allah reward you.

A: If the reality is as you mentioned; that the Imam offered the four rak`ahs of the `Asr prayer then rose up and offered a fifth, and some of the followers said, 'Subhan Allah' out loud but he did not respond to them, then those who sat down did the right thing and those who followed him were wrong. However, the prayer of either is correct. This will hold true if the Imam (Part No. 7; Page No. 132) thought that he was right and the followers did not know that it was an extra Rak`ah, or they knew but thought that they had to follow him. In situations like this, the Imam should sit down in response to those who say, 'Subhan Allah,' if he does not think that he was correct. This is because standing up will result in offering an extra Rak`ah. What he said i.e. that he cannot move from an obligation to an integral part of prayer has no grounds.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.