In another wording, “And beyond that there is not even a mustard seed of faith.” (1) This, too, shows that faith can diminish until it is no heavier than a single mustard seed.

Likewise, the sound hadith states, “Bring out of the Fire whoever has in his heart the very least—indeed, the merest weight—of a mustard seed of faith.” (2)

Thus, faith is utterance with the tongue, conviction in the heart, and action with the limbs; it increases through obedience and decreases through disobedience. This is the correct definition established by the Qur’an and the Sunnah.

Accordingly, it is not—as the Hanafīs say—merely speech of the tongue and belief in the heart; nor—as the Karāmiyyah claim—speech of the tongue alone; nor—as the Ashʿarīs assert—only the heart’s affirmation; nor—as the Jahmiyyah maintain—mere inner knowledge.

The Murjiʾah are four factions, the most extreme of them being the Jahmiyyah. On their view, Pharaoh would count as a believer, for he possessed knowledge, and even Satan would be a believer, because he, too, knew in his heart.

According to the Ashʿarīs, since faith is nothing but inner affirmation, Abū Lahab, Abū Ṭālib, Abū Jahl, and all the other idolaters would likewise be believers, because they—