Is it permissible to pray behind Ash'aris, even though they deny God's attributes, defame Mu'awiyah, and differ in their belief regarding divine decree, and despite the existence of fatwas that declare one who contradicts God's attributes and has had the proof established against him to be a disbeliever, and that declare one who denies the attribute of exaltedness (al-uluw) after the proof has been established to be a disbeliever, and given that Imam Ahmad and Shaykh al-Islam Ibn Taymiyyah held the view that one should not pray behind someone whose innovation constitutes disbelief?

A person who commits a heresy that necessitates excommunication is not to be declared an unbeliever until a proof has been established against them. Examples of such heresies include seeking aid from the dead, denying the divine attributes, secularism, and others. Praying behind someone who commits a heresy that necessitates excommunication is not permissible if one is able to pray behind someone else. However, if that is not possible, as in the case of Friday prayers and Eid prayers, one may pray behind them, unless their disbelief has been individually established. As for the Ash'aris, they are mistaken in their interpretation of some attributes, but they are not unbelievers. No scholar has ever declared them unbelievers, due to the interpretive nature of their statements, which precludes excommunication. What has been attributed to Al-Shafi'i regarding the excommunication of those who contradict the divine names and attributes is not authentically reported. Even if it were, such a person would be excused by ignorance before the proof is established.