His prayer is valid but you should be more careful about your own prayer
as it seems that you are paying more attention to your surroundings
rather than your own prayer.

The imam who lead the jummuah prayer today tends to move during his qiyam ( like rocking on his heels). It is minor, but noticable. Is my prayer valid? Or is this from shaytan?

Prayer | September 12, 2016 2:05 pm
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In what circumstances is it obligatory to pray in the masjid? Because there is a masjid 15 min from the university but sometimes I’m in class. Do I have to leave the class? Note that there is 15(going)+15(returning)+10(of salah) minutes. Or can I pray in the university when the class is finished providing that I do not delay the time of the prayer?
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There are 4 sunnah rakats before the fard rakats of zuhr prayer, can you pray those 4 sunnah rakats together? or we need to pray them as 2 by 2?