What is the ruling on praying behind someone who says "Allah is in every place" if he is an Ash'ari or a Sufi, and is it obligatory to repeat the prayer or to seek another mosque?

The belief that Allah is in every place in His essence is a false doctrine that expels its proponent from Islam, and it entails false implications. Whoever believes this, whether a Sufi or an Ash'ari, should first be advised, have the truth explained to them, and have proof established against them, if possible, without harm. One should not rule them an unbeliever before that, as ignorance is one of the impediments to declaring someone an unbeliever. Scholars differentiate between declaring unbelief in general and declaring a specific individual an unbeliever. If, after the truth has been explained to them, they persist in their statement, then they are ruled an unbeliever, and prayer behind them is not valid. Whoever prays behind them after the proof has been established against them must repeat their prayer. Nevertheless, praying behind someone who is not an innovator is undoubtedly better and more excellent.