Allah says truly,

meaning, that their final destination and their abode will be in Sijjin, which is derived from the word prison (Sijn), and here it means straitened circumstances. Thus, Allah expresses the greatness of this matter, saying;

meaning, it is a great matter, an eternal prison, and a painful torment. Some have said that it is beneath the seventh earth. It has been mentioned previously in the lengthy Hadith of Al-Bara’ bin ‘Azib that the Prophet said,

“Allah says concerning the soul of the disbeliever, ‘Record his book in Sijjin.' And Sijjin is beneath the seventh earth.”

it is known that the destination of the wicked people will be Hell, and it is the lowest of the low. For Allah says,

{Then We reduced him to the lowest of the low. Save those who believe and do righteous deeds.} (95:5-6)

Here Allah says,

and it is full of hardship and misery. Allah says,

{And when they shall be thrown into a narrow place thereof, chained together, they will exclaim therein for destruction.} (25:13)

Then Allah says,

{A Register inscribed.} This is not an explanation of His statement,

It is only an explanation of the destination that will be recorded for them, which is Sijjin. Meaning, it is inscribed, written, and completed. No one can add to it and no one can remove anything from it. This was said by Muhammad bin Ka*b Al-Qurazi. Then Allah said,

meaning, when they come to the imprisonment, Allah threatened them with, on the Day of Judgement, and the disgraceful torment. The statement, “Woe,” has already been discussed previously and there is no need to repeat it here. Basically, it means destruction and devastation. This is like what is said, “Woe to so-and-so.” This is similar to what has been recorded in the Musnad and the Sunan collections on the authority of Bahz bin Haldm bin Mu'awiyah bin Haydah, who reported from his father, who reported from his grandfather that the Messenger of Allah said,

“Woe unto whoever speaks, and lies in order to make the people laugh. Woe unto him, woe unto him.”
Then Allah says, in explaining who are the wicked, disbelieving deniers,

meaning, they do not believe it will happen, and they do not believe in its existence. Thus, they consider it a matter that is farfetched. Allah then says,

meaning, transgressive in his actions by doing that which is forbidden and exceeding the limits when acquiring the permissible. He is a sinner in his statements, because he lies whenever he speaks, he breaks his promises whenever he makes them, and he behaves in an abusive and wicked manner whenever he argues. Concerning Allah’s statement,

meaning, whenever he hears the Words of Allah from the Messenger he denies it and has ill thoughts about it. Thus, he believes that it is a collection gathered from the books of the ancients. This is as Allah says,

{And when it is said to them: "What is it that your Lord has sent down?" They say: "Tales of the men of old!"} (16:24)
Similarly Allah says,

{And they say: "Tales of the ancients, which he has written down: and they are dictated to him morning and afternoon."} (25:5)

Then Allah continues saying,

meaning, the matter is not as they claim, nor as they say: “Verily, this Qur’an is tales of the ancients.” Rather, it is the Word of Allah, His inspiration and His revelation to His Messenger. The only thing that blocked their hearts from believing in it is the dark covering cast over it from the many sins and wrong they committed that has covered up their hearts. Thus, Allah says,

This dark covering known as Rayn overcomes the hearts of the disbelievers, the covering of Ghaym is for the righteous, and the covering of Ghayn is for those who are near to Allah.

Ibn Jarir, At-Tirmidhi, An-Nisal, and Ibn Majah all recorded from Abu Hurayrah that the Prophet said,

“Verily, when the servant commits a sin, a black spot appears in his heart. If he repents from it, his heart is polished clean. However, if he increases (in the sin), the spot will continue to increase. That is the statement of Allah: {Nay! But on their hearts is the Ran (covering) which they used to earn.}”
At-Tirmidhi said, “Hasan Sahih.” The wording of An-Nasal says,

“Whenever the servant commits a wrong, a black spot is put in his heart. So, if he refrains from it, seeks forgiveness and repents, his heart is polished clean. But if he returns to the sin, the spot will increase until it overcomes his (entire) heart, and this is the Ran that Allah mentions when He says: {Nay, but on their hearts is the Ran (covering) which they used to earn.}”

Concerning Allah’s statement.

meaning, they will have a place on the Day of Judgement, and lodging in Sijjin. Along with this they will be veiled from seeing their Lord and Creator on the Day of Judgement. Imam Abu ‘Abdullah Ash-Shafil said, “In this Ayah is a proof that the believers will see Him (Allah), the Mighty and Sublime, on that Day.”