Ṣaḥīḥ al-Bukhārī Ḥadīth [41] – The Reward of Good Deeds is Ten Times…

قَالَ مَالِكٌ: أَخْبَرَنِي زَيْدُ بْنُ أَسْلَمَ، أَنَّ عَطَاءَ بْنَ يَسَارٍ، أَخْبَرَهُ أَنَّ أَبَا سَعِيدٍ الخُدْرِيَّ أَخْبَرَهُ أَنَّهُ سَمِعَ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقُولُ: إِذَا أَسْلَمَ العَبْدُ فَحَسُنَ إِسْلاَمُهُ، يُكَفِّرُ اللَّهُ عَنْهُ كُلَّ سَيِّئَةٍ كَانَ زَلَفَهَا، وَكَانَ بَعْدَ ذَلِكَ القِصَاصُ: الحَسَنَةُ بِعَشْرِ أَمْثَالِهَا إِلَى سَبْعِ مِائَةِ ضِعْفٍ، وَالسَّيِّئَةُ بِمِثْلِهَا إِلَّا أَنْ يَتَجَاوَزَ اللَّهُ عَنْهَا

Book [2]: Belief
Chapter [31]: (What is said regarding the superiority of) a person who embraces Islām sincerely.

Ḥadīth [41]: It is narrated on the authority of Abū Sa’īd al-Khudrī (may Allāh be pleased with him) that he said: The Messenger of Allāh (peace and blessings of Allāh be upon him) said: “If a person embraces Islām sincerely, then Allāh shall forgive all his past sins, and after that starts the settlement of accounts, the reward of his good deeds will be ten times to seven hundred times for each good deed and one evil deed will be recorded as it is unless Allāh forgives it.”