In The Name of Allaah, The Most Merciful, The Bestower of Mercy.

Allaah [The Exalted] said:

وَلَوِ ٱتَّبَعَ ٱلۡحَقُّ أَهۡوَآءَهُمۡ لَفَسَدَتِ ٱلسَّمَـٰوَٲتُ وَٱلۡأَرۡضُ وَمَن فِيهِنَّ‌ۚ بَلۡ أَتَيۡنَـٰهُم بِذِڪۡرِهِمۡ فَهُمۡ عَن ذِكۡرِهِم مُّعۡرِضُونَ

And if the truth had been in accordance with their desires, verily, the heavens and the earth, and whosoever is therein would have been ruined! Nay, We have brought them their reminder, but they turn away from their reminder. [Surah Al-Muminoon. Aayah 71]

[وَلَوِ ٱتَّبَعَ ٱلۡحَقُّ أَهۡوَآءَهُمۡ لَفَسَدَتِ ٱلسَّمَـٰوَٲتُ وَٱلۡأَرۡضُ وَمَن فِيهِنَّ‌ۚ – And if the truth had been in accordance with their desires, verily, the heavens and the earth, and whosoever is therein would have been ruined!] – Meaning, on the basis of the fact that their desires are attached to wrongdoing, disbelief, and corruption that emanates from (evil) manners and deeds. So, if the truth had been in accordance to their desires, the heavens and the earth would have been ruined due to corrupt behaviour, and management of its affairs based on wrong doing and inequity. That is because the heavens and the earth cannot be maintained in (upright) order except through truth and justice.

[بَلۡ أَتَيۡنَـٰهُم بِذِڪۡرِهِمۡ – Nay, We have brought them their reminder]- Meaning, this Qur’aan that reminds them of every good thing, in which there is self-esteem and honour for them if they act upon it, and will become leaders of humankind by way of that. (1)

[فَهُمۡ عَن ذِكۡرِهِم مُّعۡرِضُونَ – but they turn away from their reminder] – Meaning, they have turmed away from that which will bring about nobility in this life and the next. (2)

Allaah [The Exalted] said: [إِن يَتَّبِعُونَ إِلَّا ٱلظَّنَّ وَمَا تَهۡوَى ٱلۡأَنفُسُ‌ۖ – They follow but a guess and that which they themselves desire].

There is a tremendous benefit derived from this Aayah, because the one deprived of sound faith and the sound creed sent down as revelation by Allaah- The Lord of the entire existence, then his affair is one of two: corrupt knowledge or corrupt Intent. Corrupt knowledge occurs as a result of following conjecture and corrupt intent occurs as a result of following desires, or a person may combine both of them. Another benefit derived from this Aayah is that the rectification or well-being of a person cannot be attained except by way of two affairs: upright knowledge and upright Intent. This is why Imaam Ibnul Qayyim stated in Miftaah Daarus Sa’aadah that a person is in need of two things: sound knowledge by way of which he is (rightly) guided and lofty aspiration by way of which he is urged towards (good), because it maybe that a person has beneficial knowledge but not upright intent and aspiration. Therefore, one cannot be upright except by way of upright knowledge and intent. Sound knowledge is corrupted through following conjecture and sound intent is corrupted through following the desires of one’s soul.

Allaah [The Exalted] stated about the Messenger [peace and blessings of Allaah be upon him]: [مَا ضَلَّ صَاحِبُكُمۡ وَمَا غَوَىٰ-Your companion (Muhammad) has neither gone astray nor has erred]. That is because the Daal [misguided person] is one whose knowledge is corrupted and the Ghaawiy [astray one] is the one whose intent is corrupted. Also, the Prophet described his four khulafaa [Abu Bakr, Umar, Uthmaan and Ali] with the words Raashideen and Mahdiyyeen, because the Raashid [The one who is steadfast upon the right path and is firmly established upon it] is the opposite of the Ghaawiy [The one who strays from the right path or conduct], and the Mahdee [The one guided to the path of truth and willingly adheres to it] is the opposite of the Daallun [the misguided one, especially in knowledge and creed]. (3)

Allaah [The Exalted] said:

أَفَمَن زُيِّنَ لَهُ سُوءُ عَمَلِهِ فَرَآهُ حَسَنًا ۖ فَإِنَّ اللَّهَ يُضِلُّ مَن يَشَاءُ وَيَهْدِي مَن يَشَاءُ ۖ فَلَا تَذْهَبْ نَفْسُكَ عَلَيْهِمْ حَسَرَاتٍ ۚ إِنَّ اللَّهَ عَلِيمٌ بِمَا يَصْنَعُونَ

Is he, then, to whom the evil of his deeds made fair-seeming, so that he considers it as good? Verily, Allah sends astray whom He wills, and guides whom He wills. So destroy not yourself (O Muhammad) in sorrow for them. Truly, Allah is the All-Knower of what they do! [Surah Al-Faatir. Aayah 8]

[أَفَمَن زُيِّنَ لَهُ سُوءُ  – Is he, then, to whom the evil of his deeds made fair-seeming] -Meaning, his evil and repugnant deeds have been made fair-seeming to him by shaytaan and beautified in his eyes; [ فَرَآهُ حَسَنًا- so that he considers it as good] -Meaning, considers his evil and repugnant deeds to be good like the one whom Allaah has guided to the straight path and the upright religion, but are the two the same? The first one commits evil deeds, considers truth to be falsehood and falsehood to be truth, and the second person performs good deeds, considers truth to be truth and falsehood to be falsehood. However, guidance is in the hands of Allaah:

[ فَإِنَّ اللَّهَ يُضِلُّ مَن يَشَاءُ وَيَهْدِي مَن يَشَاءُ ۖ فَلَا تَذْهَبْ نَفْسُكَ عَلَيْهِمْ حَسَرَاتٍ – Verily, Allah sends astray whom He wills, and guides whom He wills. So destroy not yourself (O Muhammad) in sorrow for them]- Meaning, the misguided ones to whom their evil deeds are made fair-seeming and shaytaan hinders them from the truth. Therefore, there is nothing obligated on you (O Muhammad) except to convey the message and there is nothing on you regarding their guidance, rather Allaah is the one who will recompense them for their deeds. [ إِنَّ اللَّهَ عَلِيمٌ بِمَا يَصْنَعُونَ- Truly, Allah is the All-Knower of what they do]. (4)

Ibn Abbaas said: This Aayah was revealed concerning Abu Jahl and the idolaters of Makkah. Sa’eed Bin Jubair said: This was revealed concerning the people of religious innovations and evil desires. Qataadah said: And from them are the khawaarij who make lawful the spilling of the blood of the Muslims and confiscating their wealth. As for the people of the Kabaa’ir (i.e. those sinful Muslims who commit major sins), they are not from them (i.e. not from those whom the evil of their deeds are made fair-seeming) because they do not declare the major sins to be lawful. The one to whom doubts are made fair-seeming and is submerged in it, and his deeds are made fair-seeming to him, so that he considers it as good, shaytaan makes it fair-seeming to him through whispers”. (5)

Shaikhul Islaam Ibn Taymiyyah said: The pious predecessors named Ahlul Bidah Wal Furqah [the people of religious innovations and blameworthy splitting]- those who oppose the Book and the Sunnah- as Ahlul Ahwaa [the people of desires], because they accept what they love and reject what they hate based on their desires without guidance from Allaah. (6)

[Ref 1: An Excerpt from Tafseer As-Sadi. Slightly paraphrased]
[Ref 2: An Excerpt from Zaadul Maseer Fee Ilmit Tafseer. By Imaam Ibnul Jawzi]
[Ref 3: An Excerpt from Sharh Kitaab At-Tawheed. Lesson 4. By Shaikh Abdur Razzaaq Al-Badr. Slightly paraphrased]

[Ref 4 An Excerpt from Tafseer As-Sadi. Slightly paraphrased]

[Ref 5: Tafseer Al-Baghawi 3/689]

[Ref 6: An Excerpt from Majmoo Al-Fataawaa 4/189-190]