How can the prophetic narrations that urge adherence to the group be reconciled with what the questioner mentioned about the invalidity of the Shafi’i prayer behind the Hanafi in certain issues? And is what he concluded – that each madhhab prays only behind an imam from its own madhhab – correct?

The issues are summarized as the permissibility of a congregant praying behind an imam who differs with him on matters of ablution (wudu) or behind a non-disbelieving innovator (mubtadi').

Regarding the first issue, the preponderant opinion is that the validity depends on the imam's conviction. It is permissible for the congregant to pray behind him, even if the congregant believes that the imam has done something that invalidates his ablution, because the imam's error does not extend to the congregant. This is the view of the majority of the Salaf.

Regarding the second issue, prayer behind a Muslim who is disobedient due to innovation or sin is valid if it is not possible to pray with someone else, or if abandoning it would cause discord and division, because the prayer of a transgressor (fasiq) and an innovator is intrinsically valid.