What is the ruling on praying in a mosque, part of which was built with money from Shiites, and in which both Shiites and Salafis pray, and in which Shiite rituals are performed, knowing that it is the only mosque available and abandoning it will leave the arena to the Shiites?

The participation of Shiites in building a mosque does not prevent prayer in it, because the mosque belongs to Allah, and it is permissible for both a Muslim and a disbeliever to build it. Sunnis are more entitled to cling to it and contend with the people of innovation over it. If they can gain control of a part of it, such as the second floor, that is better than leaving it entirely to them, because abandoning a place to the people of innovation leads to the establishment of their innovations and deterring people from the path of Allah. "Masjid al-Dirar" (the Mosque of Harm) differs from competing with the people of falsehood in a mosque to reclaim a part of it for establishing the rituals of Allah.