Abdullah bin Abbas reported,

There was a group of people who had killed, and killed often, and committed adultery, and committed it often, and violated all bounds. They came to the Prophet ﷺ and said, "Muhammad, what you say and call people to is truly good, if only you would tell us that there is an expiation for what we have done."So Allah revealed, "And those who do not invoke any other god along with Allah, nor kill the soul which Allah has forbidden except by right, nor commit adultery. Whoever does that will meet a punishment. The torment will be doubled for him on the Day of Resurrection, and he will abide in it disgraced, except for the one who repents, believes, and does righteous deeds. For such people Allah will change their evil deeds into good deeds" [Furqan 25:68–70].He said, Allah will change their idolatry into faith, and their adultery into chastity.And this was revealed, "Say, my servants who have wronged yourselves beyond measure, do not despair of the mercy of Allah. Indeed Allah forgives all sins. He is the Most Forgiving, the Most Merciful" [Zumar 39:53].

عن ابن عباس

أن قوما كانوا قتلوا- فأكثروا، وزنوا فأكثروا، وانتهكوا، فأتوا النبي ﷺ فقالوا: يا محمد! إن الذي تقول وتدعو إليه لحسن، أو تخبرنا أن لما عملنا كفارة. فأنزل الله عز وجل: {والذين لا يدعون مع الله إليها ءاخر ولا يقتلون النفس التي حرم الله إلا بالحق ولا يزنون ومن يفعل ذلك يلق أثاما يضعف له العذاب يوم القيمة ويخلد فيه مهانا إلا من تاب وءامن وعمل عملا صلحا فأوليك يبدل الله سيئاتهم حسنات} [الفرقان: ٦٨- ٧٠] قال: يبدل الله شركهم إيمانا، وزناهم إحصانا. ونزلت: {قل يعبادي الذين أسرفوا على أنفسهم لا تقنطوا من رحمة الله إن الله يغفر الذنوب جميعا إنه هو الغفور الرحيم} [سورة الزمر: ٥٣].