The Call to repent before the Punishment comes

This Ayah is a call to all sinners, be they disbelievers or others, to repent and turn to Allah. This Ayah tells us that Allah, may He be blessed and exalted, will forgive all the sins of those who repent to Him and turn back to Him, no matter what or how many his sins are, even if they are like the foam of the sea. This cannot be interpreted as meaning that sins will be forgiven without repentance, because Shirk can only be forgiven for the one who repents from it. Al-Bukhari recorded that Ibn `Abbas, may Allah be pleased with him, said that some of the people of Shirk killed many people and committed Zina (illegal sexual acts) to a great extent; they came to Muhammad ﷺ and said, "What you are saying and calling us to is good; if only you could tell us that there is an expiation for what we have done." Then the following Ayat were revealed:

وَالَّذِينَ لاَ يَدْعُونَ مَعَ اللَّهِ إِلَـهَا ءَاخَرَ وَلاَ يَقْتُلُونَ النَّفْسَ الَّتِى حَرَّمَ اللَّهُ إِلاَّ بِالْحَقِّ وَلاَ يَزْنُونَ

The next three verses (56-58), beginning from: أَن تَقُولَ نَفْسٌ يَا حَسْرَ‌تَىٰ (Pity on me, because I fell short in respect of Allah... 39:56) and concluding on: مِنَ الْمُحْسِنِينَ (...become one of those who are good in deed - 39:58), have elaborated and emphasized the subject of the three verses earlier to it (53-55), that no sinner of any description should despair of the mercy of Allah, for should he repent, Allah will forgive all his past sins. But through the use of the expression: أَن تَقُولَ نَفْسٌ (lest someone should say) at the head of the three verses: 56, 57 and 58, it was reminded that the time of taubah has a deadline - it has to be well before death. If someone were to think of making his taubah after death on the Day of Judgment, or is simply filled with remorse over what awful things he had done to himself, then, that will bring him no benefit.

In this context, it has been mentioned that some disbelievers, on the Day of Judgment, would express different wishes, regretting what they had done. Someone will be filled with remorse as to why did he have to fall short in obeying the commands of Allah Ta’ ala. Then, there will be that odd person even at a place like that who would love to wriggle out of the impasse blaming his destiny for his misconduct by saying - 'Had Allah Ta’ ala given me the necessary guidance, I too would have been one of those who feared Him, but since He gave me no guidance, there was nothing I could do about it.' Still someone else would wish: 'Would that I were to be sent back into the world to become an observing believer, obeying the commandments of Allah at its best.' But, that will be a time when no wish and no remorse of any kind will work.