Masjid Dhiraar

Surah 9 V107

This is the case of a mosque built to be a base of mischief and sow disunity among muslims. This mosque was not too far from the Quba mosque.

The Prophet (sallahu alaihi wassallam) ordered the Sahabah Radiallahu anhum to destroy it.

So much was the gravity of this action, that during the time of Umar (radhi allahu anhu), he questioned the Imam of that mosque before appointing him to the Quba mosque.
Only when the Imam explained that he left the mosque once he realised what they were up to, that Umar radhi allahu anhu forgave him.