Is it permissible for a congregant to stand in front of the imam during congregational prayer, especially if the mosque is full and the worshippers are arrayed outside the mihrab or on a level advanced beyond the imam?

The preponderant opinion is the validity of prayer in front of the imam when there is an excuse, such as the mosque being too small. This is the view preferred by Sheikh Ibn Uthaymeen, as necessity calls for it on Fridays and during Hajj. The proponents of this view did not stipulate that the congregant must join the prayer after the imam has begun; rather, their prayer is valid even if they pray in front of him in the outer courtyards and begin the prayer with him from the very beginning while he is inside the mosque.