Trials of the Heart
Ibn al-Qayyirn said, whilst commenting upon the following hadîth: “Trials and tribulations will be presented to hearts, as a reed mat is interwoven stick by stick. Any heart which absorbs these trials will have a black mark put in it. However, any heart that rejects them will have a white mark put in it. The result is that hearts will be of two kinds: one white like a white stone, which will not be harmed by trials as long as the heavens and earth endure; and the other dark and rusty, like an over-turned vessel; not able to recognise the good, nor reject evil, but rather being absorbed with its desires.” 
“The fitan (trials) which are presented to the hearts – and which are the cause of its weakness – are: [i] the trials relating to shahwah (false desire) and [ii] the trials relating to shubhah (doubt) … So the first causes intentions and desires to be corrupted, whilst the second causes knowledge and beliefs to be corrupted.”  Speaking about such trials, he - rahimahullâh - said: “Hearts – when exposed to such fitan (trials) – are of two types: [The first type]: a heart, which, when exposed to such trials, absorbs it like a sponge that soaks-up water, leaving in it a black stain. Such a heart continues to soak-up the various trials that are presented to it, until it becomes dark and corrupted – which is what is meant by “an over-turned vessel”, so when this occurs, two dangerous and deadly diseases take hold of it and plunge it into destruction:
Firstly: confusing good with evil, so it neither recognises the good, nor rejects the evil. This disease may take hold of it to such an extent that it believes good to be evil; and evil to be good, Sunnah to be bid’ah (innovation); and innovations to be the Sunnah, and the truth to be falsehood; and falsehood the truth.
Secondly: judging by its whims and desires, over and against what Allâh’s Messenger sallallâhu ’alayhi wa sallam came with – being enslaved by its whims and desires and being led by them also.
[The second type]: a white heart in which the light of îmân is bright and its radiance is illuminating. So when trials are presented to such a heart, it rejects and turns away from them. This further increases its light and illumination and its strength.” 
7. Related by Muslim (no.144), from Hudhayfah radiallâhu ’anhu.
8. Ighâthatul-Luhfân (p.40).
9. Ighâthatul-Luhfân (pp. 39-40).
Al-Fawâ’id: Points of Benefit
By the Imâm – the Shaykh of Islâm – Ibn al-Qayyim al-Jawziyyah
To read this article in spanish click here