If a person converts to Islam, one reward from God is that he gets all of his past sins forgiven. What’s so special about this? Well, we have to look at this psychologically. If a person is truly good deep inside, no matter how many sins he has done, he will feel guilty. Even if he keeps sinning for years and years, he knows deep down that they are not right and he shouldn’t have done them. It becomes a burden and often the heaviness of the sins is what makes people depressed, lose sleep, and even get suicidal. They often ask themselves “How can God ever forgive me?” If they then find out that, yes indeed, He can forgive anything and everything, it finally puts their hearts at ease.

You can ask converts. Countless had similar stories. “I’ve lived a life of sins.” “I had an abortion and killed an innocent baby.” “I’ve done drugs, been involved in gangs, and even murdered people.” Then Islam gave them peace.

In fact, similar incidences happened at the time of Prophet Muhammad (ﷺ). ‘Amr ibn al-‘As (رَضِيَ ٱللَّٰهُ عَنْهُ) was a polytheist, a sinner, and an enemy of the Muslims. He said: 

“When Allah put the love of Islam into my heart, I came to the Prophet to pledge my allegiance to him. He stretched out his hand towards me, but I said, ‘I will not pledge allegiance to you, O Messenger of Allah, until you forgive me my previous sins.’ The Messenger of Allah said to me, ‘O ‘Amr, do you not know that Islam wipes out whatever sins came before it?’” 

[Narrated by Imam Ahmad, 17159]

In another incident, it is narrated that Ibn ‘Abbas (رَضِيَ ٱللَّٰهُ عَنْهُ), the cousin of the Prophet, explained that some of the polytheists did a lot of killing and committed a lot of adultery. They came to Prophet Muhammad and said, “What you say and what you are calling for is good. If only you could tell us that there is any expiation for what we have done.” Then Allah revealed in the Qur’an,

“Say: ‘O ‘Ibaadi (My slaves) who have transgressed against themselves (by committing evil deeds and sins)! Despair not of the Mercy of Allah, verily, Allah forgives all sins. Truly, He is Oft‑Forgiving, Most Merciful.

And turn in repentance and in obedience with true Faith (Islamic Monotheism) to your Lord and submit to Him before the torment comes upon you, (and) then you will not be helped…” [Qur’an 39:53-54]

That, Muslims exclaim, is part of the perfection of Islam. It’s as if God knows how hard the sins are on you and so, simply you accepting the truth and becoming Muslim will forgive them for you, relieve you of that burden, and give you a fresh start.