In The Name of Allaah, The Most Merciful, The Bestower of Mercy
Allaah [The Exalted] said:
إِنَّ ٱلۡإِنسَـٰنَ لَفِى خُسۡرٍ
إِلَّا ٱلَّذِينَ ءَامَنُواْ وَعَمِلُواْ ٱلصَّـٰلِحَـٰتِ وَتَوَاصَوۡاْ بِٱلۡحَقِّ وَتَوَاصَوۡاْ بِٱلصَّبۡرِ
By Al-‘Asr (the time). Verily! The human is in loss; except those who believe (in Islamic Monotheism) and do righteous good deeds, enjoin one another to the truth and enjoin one another to patience. [Surah Al-Asr]
Imaam Ibnul Qayyim [may Allaah have mercy upon him] said: It is not enough that they know the truth and exercise patience, rather they have to command, guide and urge one another to act upon it. And when it is the fact that others besides these people are losers, it is well known that disobedience and sins blinds the sound discernment (or perception, foresight) of the hearts, so they do not understand the truth as it should be and their strength of determination is weakened due to not exercising patience; rather indeed the heart is exposed to haphazard thoughts until its understanding goes the opposite way and likewise the person’s conduct, so he perceives falsehood as truth and truth as falsehood, good as evil and evil as good. His conduct goes the opposite way- turns away from his journey towards attaining the Pleasure of Allaah and the home of the afterlife (i.e paradise) and proceeds towards the residence of the futile souls that are pleased with the worldly life, satisfied with it, heedless of Allaah and His signs (revelation, lessons etc), and abandons preparing to meet Allaah (i.e. by way of upright believe and righteous deeds). (I) Had there not been any other punishment due to one’s sins other than this, it would have been (enough as a) demand that one abandons this path and distance from it. And Allaah’s Aid sought! (1)
Footnote (I): The Imaam also stated in Al-Fawaa’id pages 137-137: if a person prefers what is deficient and will eventually cease to exist, then that is either because the virtue of (the afterlife) is not manifested to him or due to a lack of desiring what is more virtuous. Both these two states are an indication of weakness in Eemaan, intellect and clear-sightedness, because indeed the one who desires the Dunyah- the one who gives it precedence and is eager for it, either he testifies that there is what is more virtuous and everlasting, or he does not testify. If he does not testify (i.e. that the Aakhirah is more virtuous and everlasting), he is completely devoid of Eemaan; however if he testifies (i.e. that the Aakhirah is more virtuous and everlasting) but does not give it precedence, then his intellect is corrupt and he has made an evil choice for himself. These two (testimonies) are inevitable and a servant cannot escape them, because giving precedence to the Dunyah over the Aakhirah is either due to corruption in Eemaan or due to corruption of one’s intellect, and in many cases both of them are combined together (in a person).
[An Excerpt from Al-Jawaab Al-Kaafi 135-136. slightly paraphrased]