Reference: Majmoo’ Fataawa wa Rasaa.il Muhammad ibn Saalih al-‘Uthaymeen – Volume 13, Fatwa No.418
Question: If the congregation became crowded in the masjid, then is it permissible for some of them to pray [immediately] to the right of the imaam and his left. And is the one who prays [immediately] to the right of the imaam regarded as having attained the reward for praying in the first row?
Response: If the congregation became crowded in the masjid, then there is no harm in praying [immediately] to the right of the imaam or to his left, or to the right of him only, and those who do so are not regarded as [being in] the first row, because the first row is the first row behind the imaam.
