Following the Imam
Ibn Masud (radi Allahu anhu) said: One night I joined the Prophet (sal Allahu alaihi wa sallam) in his (optional) Salat. He prolonged the standing so much that I thought of doing something evil. He was asked: “What did you intend to do?” He replied: “To sit down and leave him.”
[Sahih al-Bukhari and Muslim]
1. This Hadith makes it evident that the opposition of the Imam (one who leads the prayer) is an evil act because one is ordered to follow him in the prayers.
2. It is permissible to ask clarification of something which is ambiguous or abstruse.
And Allah Knows Best!