that is firm, in this worldly life and in the Hereafter, is like general knowledge of which one is heedless, recalling it to mind when something causes him to doubt it, then turning to Allah to dispel that doubt. Moreover, people differ in the states and deeds of their hearts—such as love for Allah and His Messenger, fear of Allah, reliance upon Him, patience with His decree, gratitude to Him, turning to Him in repentance, and devotion to Him alone in their deeds—to an extent known only to Allah, Mighty and Majestic. Whoever denies these differences is either ignorant and has not grasped the matter, or is obstinately denying it.
Imam Ahmad said:
“If they claim that they do not accept that faith increases because they do not know what its increase is and because it has no defined limit, what do they say about Allah’s prophets, scriptures, and messengers? Do they acknowledge them in general and maintain that this is part of faith?
“If they say, ‘Yes,’ they should be asked: ‘Can you enumerate them and do you know their number? Do they not simply acknowledge them in general and then refrain from specifying their number? The same applies to the increase of faith.’”
Ahmad explained that their not knowing the ultimate extent of faith’s increase does not prevent them from acknowledging it in general, just as they believe in the prophets and scriptures without knowing the number of scriptures and messengers. What Ahmad, Muhammad ibn Nasr, and others mentioned makes clear that they did not know the number of scriptures and messengers, and that they did not regard the hadith of Abū Dharr on this subject as established.
As for those who equate Islam with faith and say, “Allah has applied the term faith to what He has called Islam, and the term Islam to what He has called faith,” this is not so, for Allah