Khaythamah ibn ‘Abd al-Rahmān said: “Faith grows fat in times of abundance and lean in times of drought. Its abundance is righteous deeds, and its drought is sins and disobedience.”

One of the early generations was asked: “Does faith increase and decrease?” He replied: “Yes. It increases until it becomes like mountains, and decreases until it becomes like specks of dust.”

In the authentic hadith narrated by Hudhayfah:

“A man will be spoken of in these terms: ‘How strong he is! How clever he is! How intelligent he is!’ Yet there will not be a mustard seed’s weight of faith in his heart.”

In another authentic hadith narrated by him:

“Trials are presented to hearts as a reed mat is woven, reed by reed. Any heart that absorbs them is marked with a black spot, while any heart that rejects them is marked with a white spot, until hearts become of two kinds: one white like a smooth stone, unharmed by any trial for as long as the heavens and the earth endure; the other dusky black, like a cup tipped over, neither recognizing good nor rejecting evil, except as dictated by the desires it has absorbed.”

The hadith concerning the seventy thousand who enter Paradise without being brought to account is sufficient evidence. Indeed, it is among the strongest proofs that faith increases and decreases, for it describes them as possessing strong and increased faith through those qualities which indicate the strength of their faith and their reliance upon Allah in all their affairs.

Abū Nu‘aym narrated through al-Layth ibn Sa‘d, from Yazīd ibn ‘Abd Allāh al-Yazanī: “Abū Rāfi‘ heard a man relate that he had asked the Messenger of Allah, may Allah bless him and grant him peace, about faith. He replied: ‘Would you like me to tell you what true faith is?’ The man said: ‘Yes.’ He said: ‘When you do wrong or wrong anyone—your male slave, your female slave, or anyone else—you grieve and are distressed by it.