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

Commentary

Verse 53 opens with the words: قُلْ يَا عِبَادِيَ الَّذِينَ أَسْرَ‌فُوا (0 servants of Mine who have acted recklessly against their own selves, do not despair of Allah's mercy. Surely, Allah will forgive all sins.). Taba` i, Said Ibn Jubayr reports from Sayyidna Ibn ` Abbas ؓ that there were some people who had killed a lot of people unjustly and had committed a lot of shameful acts. They came to the Holy Prophet ﷺ and submitted before him, 'The religion you invite us to is, no doubt, very good, but we have a problem. We think about all those major sins we have already committed. Now if we were to become Muslims, do you hope that our repentance will be accepted?' Thereupon, Allah Ta’ ala revealed this verse to the Holy Prophet ﷺ - reported by al-Bukhari in that sense (al-Qurtubi).