How can the deeds of the heart be reformed, and what does it mean for "one's heart to be sealed"?

The causes of the sealing of the heart are sins and transgressions that displease Allah. The more these sins increase without repentance, the more black spots accumulate in the heart until they cover it, which is known as "al-ran" (rust/stain).

The sign of a sealed heart is the failure to respond to Allah's commands and prohibitions, and the pursuit of desires and whims. Ibn Al-Qayyim mentioned types of hearts: 1. The Sound Heart (Al-Qalb Al-Saleem): This is the heart that is free from every desire that contradicts Allah's command and prohibition, and from every doubt that opposes His revelation. 2. The Dead Heart (Al-Qalb Al-Mayyit): This is the heart that worships other than Allah in love, fear, and hope, and its whims are its imam, and its desires are its guide. 3. The Sick Heart (Al-Qalb Al-Mareed): This is the heart that has both life and ailment, with the love of Allah and the love of desires contending within it.

The most important cure for hearts is reading the Holy Quran, for it is a healing for what is in the breasts, removing doubt, polytheism, and the diseases of doubts and desires. And Allah does not look at forms or wealth, but rather at hearts and deeds.