What is the ruling on placing a barrier on both sides of the rows in the mosque for the passage of worshippers, so that they do not interrupt the prayer of those who joined late?

It is permissible to place a barrier in a large mosque if there is a need for it, to facilitate the exit of worshippers from the front rows without passing in front of those praying. However, this is not permissible in a small mosque because it would restrict the prayer space. The fundamental principle is not to alter an endowment unless there is an overriding benefit. It is permissible to change the condition set by the endower to what is more beneficial, and changing the form of an endowment for an overriding benefit is permissible.