The ruling on the ma'mum praying outside the mosque while hearing the imam's voice

Question:
I say, Honorable Shaykh, may Allah grant you success, is it valid for a follower to pray outside the mosque while he hears the voice of the imam, as the worshippers in this mosque do in the Friday prayer?

Answer:
If they can see the imam or the followers through a door opening or a window in the door, there is no problem. But if they cannot see anyone, neither the imam nor the followers, and they are outside the mosque, they should not sit there; this is not permissible. Even if they can hear the recitation, they should go to another mosque that has space. As for people crowding around a mosque and praying in the streets, while some mosques have no shortage of space or only a few people in them, this is not permissible. They should pray in all the mosques that have empty space.