What is the ruling on the prayer of one who intended to shorten the Maghrib prayer but prayed it two rak'ahs out of forgetfulness, then completed the third rak'ah after being reminded and after the taslim, and performed the prostration of forgetfulness? And is it obligatory to repeat the 'Isha' prayer if it was combined with it?

If a traveler intends to shorten the prayer (qasr) when it is not permissible for him to do so, then his prayer is not valid as an obligatory prayer, and he must repeat it, as well as repeat the second prayer that he combined with it. As for the congregants (ma'mumin), they are not required to repeat their prayers, because the intention of the Imam is a hidden matter of which they have no knowledge.