قُلْ يَا عِبَادِيَ الَّذِينَ أَسْرَفُوا عَلَىٰ أَنفُسِهِمْ لَا تَقْنَطُوا مِن رَّحْمَةِ اللَّهِ ۚ إِنَّ اللَّهَ يَغْفِرُ الذُّنُوبَ جَمِيعًا ۚ إِنَّهُ هُوَ الْغَفُورُ الرَّحِيمُ

When those who possess sensitive hearts are blessed with a deep realisation of God (ma‘rifah), they start becoming worried as to what would happen about their past sins. Similarly, even after adopting a God-fearing way of life, a man is likely to display shortcomings from time to time, and his sensitive nature makes him worry again on this account. These feelings in some people can become so intense as to cause a deep sense of frustration. For such people, God has declared in His Book that they should firmly believe that their God is Forgiving and Merciful. He does not look at a man’s past but at his present. He does not look to his outward form but at his inner soul. He treats a man with broad-mindedness and not with petty-mindedness. That is why, when a man turns towards Him, He once again takes him into the fold of His Mercy, howsoever big a blunder the man might have committed.

— Source: Tazkirul Quran (Maulana Wahiduddin Khan) via Quran.com (39:53)