that prayer behind a Hanafī is invalid even if he performs all the obligatory acts, because he performs them without believing them to be obligatory. Anyone who holds this view is more deserving of being called to repent—as adherents of religious innovation are—than of having his dissent accorded weight. For Muslims have always prayed behind one another, from the time of the Prophet (peace and blessings be upon him) and his caliphs. Most prayer leaders do not distinguish between obligatory and recommended acts; rather, they perform the prayer as prescribed. Had knowledge of this distinction been obligatory, the prayers of most Muslims would have been invalid, and taking precautions would not have been possible. Many of these matters are disputed, and the evidence concerning them is not readily apparent. The most a devout person can do is take precautions in light of the disagreement, without being certain which of the two views is correct.

If certainty about either view were obligatory, most people would be unable to attain it. The proponent of this view himself relies on nothing more than following the authority of certain jurists. Were he asked to produce scriptural evidence establishing that his imam’s position, rather than another’s, is correct, he would be unable to do so. This is why the dissent of someone like him carries no weight: he is not qualified to exercise independent juristic reasoning.

The second situation:

The follower is certain that the imam has done something that, in the follower’s view, prevents him from praying validly: for example, the imam touches his penis, touches women with desire, undergoes cupping or bloodletting, or vomits, and then prays without renewing his ablution. There is a well-known disagreement concerning this situation. One of the two views is that the follower’s prayer is invalid because he believes his imam’s prayer to be invalid. This is the view held by some followers of Abū Hanīfah, al-Shāfiʿī, and Ahmad.