Sincere repentance (tawbah)

وَإِذَا جَآءَكَ ٱلَّذِينَ يُؤْمِنُونَ بِـَٔايَـٰتِنَا فَقُلْ سَلَـٰمٌ عَلَيْكُمْ ۖ كَتَبَ رَبُّكُمْ عَلَىٰ نَفْسِهِ ٱلرَّحْمَةَ ۖ أَنَّهُۥ مَنْ عَمِلَ مِنكُمْ سُوٓءًۢا بِجَهَـٰلَةٍ ثُمَّ تَابَ مِنۢ بَعْدِهِۦ وَأَصْلَحَ فَأَنَّهُۥ غَفُورٌ رَّحِيمٌ

And when those come to you who believe in Our verses, say, "Peace be upon you. Your Lord has decreed upon Himself mercy: that any of you who does wrong out of ignorance and then repents after that and corrects himself - indeed, He is Forgiving and Merciful."

يَـٰٓأَيُّهَا ٱلنَّبِىُّ قُل لِّمَن فِىٓ أَيْدِيكُم مِّنَ ٱلْأَسْرَىٰٓ إِن يَعْلَمِ ٱللَّهُ فِى قُلُوبِكُمْ خَيْرًا يُؤْتِكُمْ خَيْرًا مِّمَّآ أُخِذَ مِنكُمْ وَيَغْفِرْ لَكُمْ ۗ وَٱللَّهُ غَفُورٌ رَّحِيمٌ

O Prophet, say to whoever is in your hands of the captives, "If Allāh knows [any] good in your hearts, He will give you [something] better than what was taken from you, and He will forgive you; and Allāh is Forgiving and Merciful."