Just as the heart may be described in
    terms of being alive or dead, it may also be regarded as belonging to one of three types;
    these are the healthy heart, the dead heart, and the sick heart.
The Healthy Heart
On the Day of Resurrection, only those who come to
    Allah with a healthy heart will be saved. Allah says:
"The day on which neither
    wealth nor sons will be of any use, except for whoever brings to Allah a sound heart.
    (26:88-89)"
In defining the healthy heart, the following has
    been said: "It is a heart cleansed from any passion that challenges what Allah
    commands, or disputes what He forbids. It is free from any impulses which contradict His
    good. As a result, it is safeguarded against the worship of anything other than Him, and
    seeks the judgement of no other except that of His Messenger 
. Its services are exclusively reserved for Allah, willingly and
    lovingly, with total reliance, relating all matters to Him, in fear, hope and sincere
    dedication. When it loves, its love is in the way of Allah. If it detests, it detests in
    the lght of what He detests. When it gives, it gives for Allah. If it witoholds, it
    withholds for Allah. Nevertheless, all this will not suffice for its salvation until it is
    free from following, or taking as its guide, anyone other than His Messenger 
." A servant with a healthy heart must dedicate it to
    its journey's end and not base his actions and speech on those of any other person except
    Allah's Messenger 
. He must not give
    precedence to any other faith or words or deeds over those of Allah and His Messenger, may
    Allah bless him and grant him peace. Allah says:
"Oh you who believe, do not
    put yourselves above Allah and His Messenger, but fear Allah, for Allah is Hearing,
    Knowing. (49:1)" 
The Dead Heart
This is the opposite of the healthy heart. It does
    not know its Lord and does not worship Him as He commands, in the way which He likes, and
    with which He is pleased. It clings instead to its lusts and desires, even if these are
    likely to incur Allah's displeasure and wrath. It worships things other than Allah, and
    its loves and its hatreds, and its giving and its withholding, arise from its whims, which
    are of paramount importance to it and preferred above the pleasure of Allah. Its whims are
    its imam. Its lust is its guide. Its ignorance is its leader. Its crude impulses are its
    impetus. It is immersed in its concern with worldly objectives. It is drunk with its own
    fancies and its love for hasty, fleeting pleasures. It is called to Allah and the akhira
    from a distance but it does not respond to advice, and instead it follows any scheming,
    cunning shayton. Life angers and pleases it, and passion makes it deaf and blind (1) to
    anything except what is evil.
To associate and keep company with the owner of such
    a heart is to tempt illness: living with him is like taking poison, and befriending him
    means utter destruction.
The Sick Heart
This is a heart with life in it, as well as illness.
    The former sustains it at one moment, the latter at another, and it follows whichever one
    of the two manages to dominate it. It has love for Allah, faith in Him, sincerity towards
    Him, and reliance upon Him, and these are what give it life. It also has a craving for
    lust and pleasure, and prefers them and strives to experience them. It is full of
    self-admiration, which can lead to its own destruction. It listens to two callers: one
    calling it to Allah and His Prophet 
 and
    the akhira; and the other calling it to the fleeting pleasures of this world. It responds
    to whichever one of the two happens to have most influence over it at the time.
The first heart is alive, submitted to Allah,
    humble, sensitive and aware; the second is brittle and dead; the third wavers between
    either its safety or its ruin.
Notes:
1. It has been related on the authority of
    Abu'd-Darda' that the Messenger of Allah 
    said, "Your love for something that makes you blind and deaf." Abu Daw'ud,
    al-Adab, 14/38; Ahmad, al-Musnad, 5/194. The hadith is classified as hasan.