Abdur Rahman ibn Awf reported: The Messenger of Allah, peace and blessings be upon him, said, “Verily, Ramadan is a month in which Allah Almighty has obligated its fasting. I have instituted for Muslims the practice of prayer at night. Thus, whoever fasts it with faith and expecting reward will be rid of sins like the day he was born from his mother.”
Source: Musnad Aḥmad 1688
Grade: Sahih (authentic) according to Ahmad Shakir
عن عبد الرحمن بن عوف قَالَ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِنَّ رَمَضَانَ شَهْرٌ افْتَرَضَ اللَّهُ عَزَّ وَجَلَّ صِيَامَهُ وَإِنِّي سَنَنْتُ لِلْمُسْلِمِينَ قِيَامَهُ فَمَنْ صَامَهُ إِيمَانًا وَاحْتِسَابًا خَرَجَ مِنْ الذُّنُوبِ كَيَوْمِ وَلَدَتْهُ أُمُّهُ
1688 مسند أحمد
2/320 المحدث أحمد شاكر خلاصة حكم المحدث إسناده صحيح في مسند أحمد