وَعَنْ أَبِي أَيُّوبَ اَلْأَنْصَارِيِّ رضى الله عنه
أَنَّ رَسُولَ اَللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «مَنْ صَامَ رَمَضَانَ، ثُمَّ أَتْبَعَهُ سِتًّا مِنْ شَوَّالٍ كَانَ كَصِيَامِ اَلدَّهْرِ»
“Whoever fasts during the month of Ramadan and then follows it with six days of Shawwal will be (rewarded) as if he had fasted the entire year.” Related by Muslim.
Bulugh al-Maram 789, Book 5, Fasting, Hadith 32. 1 min read