The Worst People are Those Who turn away after being reminded
Allah says, `Who among My creatures does more wrong than one who is reminded of the signs of Allah then turns away from them,' i.e., ignores them and does not listen or pay attention to them.
وَنَسِىَ مَا قَدَّمَتْ يَدَاهُ
(forgetting what his hands have sent forth.) means, bad deeds and evil actions.
إِنَّا جَعَلْنَا عَلَى قُلُوبِهِمْ
(Truly, We have set over their hearts) means, the hearts of these people,
أَكِنَّةً
(Akinnah) means, coverings.
أَن يَفْقَهُوهُ
(lest they should understand this,) means, so that they will not understand this Qur'an and its clear Message
وَفِى ءَاذَانِهِمْ وَقْرًا
(and in their ears, deafness.) means that they will be deaf in an abstract way, to guidance.
The statement: وَكَانَ الْإِنسَانُ أَكْثَرَ شَيْءٍ جَدَلًا (And man is the most quarrel-some of all things - 54) has been testified through a Hadith narrated by Sayyidna 'Anas ؓ in which the Holy Prophet ﷺ has been reported to have said, "On the day of Qiyamah, a man from among the disbelievers will be brought forth. He will be asked, 'what was your response to the messenger We had sent to you?' He will say, '0 my Lord, as for me, I did believe in You and in Your messenger too and that I obeyed him in everything I did.' Allah Ta` ala will say, 'here is your book of deeds before you. All this you say is not there.' This man will say, 'I do not believe in this book of deeds.' Allah Ta` ala will say, 'what about these angels of Ours? They used to watch you. They bear witness against you. This man will say, 'I do not accept their testimony as well, nor do I know them, nor have I seen them while I was doing what I did.' Allah Ta` ala will say, 'if so, this Preserved Tablet (اَلَّوح المَحفُوظ) is before you. Written here too is the same thing about you.' He will say, 'my Lord, have You granted me asylum from injustice or have you not?' Allah Ta` ala will say, 'Of course, you have your refuge against injustice with Us.' So then, he will say, '0 my Lord, how can I accept the verdict of those unseen witnesses I am not familiar with at all? As for me, I can only accept a witness that comes from my own person.' At that time, his mouth will be sealed, and his hands and feet will bear witness against his kufr and shirk. After that, he will be released and thrown into the Hell. (The subject matter of this narrative has been reported in Sahih Muslim, also from Sayyidna Anas ؓ - al-Qurtubi)
When a man flouts the Truth, but does not immediately receive the punishment for this, it makes him arrogant. The fact of his going scot free is only due to the latitude given to him during the period of trial, and not because of any real freedom. If the individual is keen to learn a lesson, he must consider the fate of his predecessors, from which he may learn how to conduct his present life. On the face of this earth, different nations and different cultures have risen from time to time and have subsequently been destroyed. When earlier generations were punished for their disobedience, why should later generations not meet the same fate?
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.