Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
tabarani:5445 – Yaḥyá b. Ayyūb al-ʿAllāf > Saʿīd b. Abū Maryam > Yaḥyá b. Ayyūb > ʿAbdullāh b. Qurayẓ > ʿAṭāʾ b. Yasār > Abū Saʿīd al-Khudrī

[Machine] Narrated Abu Sa`id Al-Khudri:

The Messenger of Allah ﷺ said, "Fasting Ramadan to Ramadan is an expiation for the sins committed between them."  

الطبراني:٥٤٤٥ – حَدَّثَنَا يَحْيَى بْنُ أَيُّوبَ الْعَلَّافُ ثنا سَعِيدُ بْنُ أَبِي مَرْيَمَ أَنَا يَحْيَى بْنُ أَيُّوبَ عَنْ عَبْدِ اللهِ بْنِ قُرَيْظٍ عَنْ عَطَاءِ بْنِ يَسَارٍ

عَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ ؓ قَالَ قَالَ رَسُولُ اللهِ ﷺ «صِيَامُ رَمَضَانَ إِلَى رَمَضَانَ كَفَّارَةُ مَا بَيْنَهُمَا»  

See similar narrations below:

Collected by Suyūṭī