Ruling on praying on the sidewalk if the mosque is full

Praying on the sidewalk is disliked (makruh) according to the majority of fuqaha’, because it is the part of the street where people walk.

The reason for it not being allowed to pray there is that it is a transgression against people’s rights, and blocks their way, and because the worshipper will be distracted by the people passing by, so his focus when praying will be reduced.

But if the Muslims need to pray on the sidewalk because the mosque is too small, and there is no other place where they can pray, then in that case there is nothing wrong with praying on the sidewalk.

See: al-Mawsu‘ah al-Fiqhiyyah (27/114; 38/367).

Shaykh Ibn ‘Uthaymin (may Allah have mercy on him) was asked:

If the mosque is too small, what is the ruling on praying in the marketplace and the area surrounding the mosque?

He replied:

There is nothing wrong with that, if someone has no choice but to pray in the marketplace or in the open spaces around the mosque. There is nothing wrong with that; even those who say that prayer is not valid if offered in the street make an exception in the case of Jumu‘ah prayer and Eid prayer, if the mosque is full and the people spill out into the marketplaces. The correct view is that an exception is made to that whenever there is a need. So if the mosque is full, there is nothing wrong with the people praying in the marketplaces."(Majmu‘ Fatawa wa Rasa’il Ibn ‘Uthaymin  12/331).

And Allah knows best.