Praying between the pillars of the masjid

Question: Is it permissible to break the row in the congregational prayer with the masjid's pillars, if it is full of worshippers?

Response: There is no doubt that it is preferable that the rows be tightly formed, (the worshippers) standing next to each other, not far apart; and this is from the Sunnah.

The Prophet (sal-Allaahu `alayhe wa sallam) ordered (the Companions) to form up tightly and to close up the gaps. And the Companions (radhi-yallaahu 'anhum) used to avoid the rows between the pillars, because doing so caused some of the ranks to be separated from others. But if there is a need for it, as in the question, due to the masjid being crowded with worshippers, then there is no objection in such a situation for them to form rows between the pillars, because exceptional circumstances are governed by special rulings, and necessity and need also have special rulings.

Shaykh Ibn 'Uthaymeen
Fataawa Islaamiyyah - Volume 1, Page 303