يَا أَيُّهَا الَّذِينَ آمَنُوا تُوبُوا إِلَى اللَّهِ تَوْبَةً نَّصُوحًا عَسَىٰ رَبُّكُمْ أَن يُكَفِّرَ عَنكُمْ سَيِّئَاتِكُمْ وَيُدْخِلَكُمْ جَنَّاتٍ تَجْرِي مِن تَحْتِهَا الْأَنْهَارُ

This verse calls believers to "sincere repentance" (tawbatan nasuha) - repentance that is genuine, complete, and resolute. Sincere repentance involves recognizing the sin, feeling genuine remorse, seeking Allah's forgiveness, and making a firm commitment not to repeat the sin. The verse promises two rewards: removal of sins (as if they never happened) and entry into Paradise with flowing rivers. The word "perhaps" (asa) doesn't indicate doubt but rather expresses hope and humility before Allah's mercy. This teaches that sincere repentance can completely erase past sins, that Allah's mercy is vast and ready to forgive those who genuinely repent, that repentance should be wholehearted and include commitment to change, and that the ultimate reward for sincere repentance is Paradise. The verse encourages believers never to despair of Allah's mercy, no matter how serious their past mistakes.