What is the ruling on praying behind an Ash'ari, and is he considered a disbeliever or an innovator, and what is the ruling of the People of the Sunnah concerning them?

The ruling on the Ash'aris and Maturidis was previously explained in Fatwa no. 35015, stating that they differed from Ahl al-Sunnah in some fundamental principles, thus placing them among the people of innovation (Mubtadi'ah). Likewise, the ruling on praying behind an innovator was clarified in Fatwa no. 42876.