Abbas - Tanwîr al-Miqbâs min Tafsîr Ibn ‘Abbâs
(And morning found those who had coveted his place) his status, standing and wealth (but yesterday crying) to one another: (Ah, welladay!) it is not as Korah said, i.e. that his wealth was his own doing, but rather (Allah enlargeth the provision for whom He will of His slaves) and in the case of Korah such wealth was a lure to perdition (and straiteneth it (for whom He will)) out of care for the person. (If Allah had not been gracious unto us) and withheld from us what He gave him, (He would have caused it to swallow us (also)) as it swallowed Korah. (Ah, welladay! the disbelievers never prosper) they will never be safe from Allah's torment.
And those who had longed to be in his place the day before, that is, only recently, were saying, ‘Alas! God expands provision for whomever He will of His servants and straitens [it], He restricts it for whomever He will (way-ka’anna: way is a noun of action, with the sense of ‘How astonished I am’, while the kāf functions as a [causative] lām, ‘because’). Had God not been gracious to us, He would have made us to be swallowed too’ (read active la-khasafa, or passive la-khusifa). Lo! indeed those who are ungrateful, for God’s grace, such as Korah, never prosper.
How Qarun and His Dwelling Place were swallowed up by the Earth
After telling us about Qarun's conceit and pride in his adornments, and how he was arrogant towards his people and transgressed against them, Allah then tells us how he and his dwelling place were swallowed up by the earth. This was also reported in the Sahih by Al-Bukhari from Salim, who said that his father told him that the Messenger of Allah said:
(While a man was dragging his lower garment, he was swallowed up and he will remain sinking down into the earth until the Day of Resurrection.) He also recorded something similar from Salim from Abu Hurayrah from the Prophet. Imam Ahmad recorded that Abu Sa`id said, "The Messenger of Allah said:
(When a man among the people who came before you went out wearing two green garments, walking proudly and arrogantly, Allah commanded the earth to swallow him up, and he will remain sinking down into it until the Day of Resurrection.) This version was recorded only by Ahmad, and its chain of narration is Hasan (sound).
(Then he had no group to help him against Allah, nor was he one of those who could save themselves.) means, his wealth, group, servants and retinue were of no avail to him; they could not protect him from the wrath and vengeance of Allah. Nor could he help himself or save himself. There was no one to help him, neither himself nor anybody else.
His People learned a Lesson from Him being swallowed up
(Those who were desirous of the life of the world, said: "Ah, would that we had the like of what Qarun has been given! Verily, he is the owner of a great fortune.'') When he was swallowed up in the earth, they began to say:
(Know you not that it is Allah Who expands the provision or restricts it to whomsoever He pleases of His servants.) Wealth does not indicate that Allah is pleased with its owner, for Allah gives and withholds, allows times of difficulty and times of ease, raises and lowers, His is the most complete wisdom and most convincing proof. According to a Hadith narrated by Ibn Mas`ud,
(Allah has alloted character among you just as He has alloted your provision. Allah gives wealth to those whom He loves and those whom He does not love, but He gives Faith only to those whom He loves.)
(Had it not been that Allah was Gracious to us, He could have caused the earth to swallow us up!) meaning, `were it not for the kindness and grace of Allah towards us, we could have been swallowed up by the earth just as he was swallowed up, because we wanted to be like him.'
وَيْكَأَنَّهُ لاَ يُفْلِحُ الْكَـفِرُونَ
(Know you not that the disbelievers will never be successful.) He was a disbeliever, and the disbelievers will never be successful before Allah in this world or in the Hereafter.
Maududi - Sayyid Abul Ala Maududi - Tafhim al-Qur'an
That is "The extension or the restriction of provisions is always according to the will of Allah, and Allah's will is determined by His own reasons and considerations. His favoring somebody with generous provisions does not necessarily mean that Allah is well pleased with him and is honoring him with gifts. Mostly it so happens that a person is under Allah's wrath, but He goes on favoring him with wore and more wealth till, at last, the same wealth causes Allah's torment to descend on him. Contrary to this, if somebody is being given restricted provisions it does not necessarily mean that Allah is displeased with him and is punishing him. Mostly the righteous then live in hardship although they are Allah's favorites, and in many cases the same hardship becomes a cause of Allah's mercy for them. Consequently, a person who does not understand this reality looks with envious eyes at the prosperity of those who actually deserve Allah's wrath."
That is, "We had the misconception, that worldly prosperity and wealth by themselves constituted real success. Therefore, we thought that Korah was highly.successful, but now we have come to know that real success is an entirely different thing, and it is never attained by the disbelievers."
This moral of the story of Korah has been mentioned only in the Qur'an. The Bible and the Talmud are without it. However, according to the details given in these books, when the Israelites left Egypt, Korah also accompanied theta along with his men, and then conspired against the Prophets Moses and Aaron and was joined in this by 250 of his followers. At last, Allah's wrath descended on him, and the earth opened up and swallowed him and his followers together with their possessions."