Must one repeat the prayer if they follow an Imam who openly declares and propagates their religious innovation (Bid'ah)?
Chapter on Imamate and Congregational Prayer
Al-Mughni
Book of Prayer
Primary text
One must repeat the prayer if one follows an Imam who manifests their innovation, speaks of it, invites others to it, or debates based on it. If the Imam does not manifest their innovation, then repetition is not obligatory upon the follower, even if the follower holds the belief internally. This is based on the definition of publicizing (*I'lan*) as making something manifest, contrasting with secrecy. The one manifesting innovation has no excuse for the follower, whose prayer is validated based on the apparent state. Ahmad commanded repetition behind the Rafidah who spoke of what was known to be deviation, and similarly behind those who call to their desires.
Supporting text
Al-Qadi defined one who openly declares deviation as one who believes in it based on evidence, while one who conceals it believes in it by mere imitation (Taqlid). There is a narration from Ahmad suggesting that prayer is never valid behind an innovator in any circumstance.