[AH] Fathul-Bari Sharah Sahi Al- Bukhari (2 vols) – فتح الباری شرح صحیح البخاری

The phenomenon of weak faith has become very widespread among Muslims, and many people complain about the hardness of their hearts. So often we hear the words, “I feel hardness in my heart,” “I do not find any joy in worship,” “I feel that my faith has hit rock bottom,” “Reading Qur’aan does not move me,” “I fall into sin so easily.” The effects of this affliction can be seen in many people, and this problem is the cause of every disaster and adversity.

One of the most important principles which must be understood in order to treat the problem of weak faith is that faith increases and decreases, or waxes and wanes. This is one of the basic principles of the ‘aqeedah of Ahl al-Sunnah wa’l-Jamaa’ah, who say that faith is something to be spoken in words, to be believed in in the heart, and to be put into action. Faith increases with obedience and decreases with disobedience.

‘… that they may grow more in Faith along with their (present) Faith…’ [al-Fath 48:4]
‘… Which of you has had his faith increased by it? …'[al-Tawbah 9:124]. aari, Fath, 1/51).