Sa`id bin Al-Musayyib said, “The clean heart is the sound heart.” This is the heart of the believer, for the heart of the disbeliever and the hypocrite is sick.
Muhammad ibn Abu Bakr (ibn Al-Qayyim) elucidates seven conditions that we, as Muslims must possess for our hearts to be saleem.
1) First is that we must establish a sense of belonging to the next world & to think about the deception of this life.
2) Our hearts must begin to feel remorse and anguish upon committing sins.
3) The third attribute of a healthy heart is that the person is more upset if they miss their daily recitation of Qur’an or Dhikr than if they lost wealth.
4) The fourth attribute of a heart that is saleem is that it finds greater pleasure in worshipping Allah, than in food and drink.
5) The fifth attribute is that the person is very concerned with doing deeds solely for the sake of Allah.
6) The sixth attribute, then of a heart that is saleem, is that when we stand up for prayer, our worries and concerns leave us.
7) One who has a healthy heart is more stingy about wasting time than the greedy or stingy person is about their wealth. We must begin to take advantage of our time, as an opportunity to do acts that will be pleasing to Allah. We cannot afford to waste time, or spend it idly.