´It was narrated from Abu Ayyub that the Messenger of Allah (ﷺ) said:` “Whoever fasts Ramadan then follows it with six days of Shawwal, it is as if he fasted for a lifetime.”
Hadith Referenceسنن ابن ماجه / كتاب الصيام / 1716
Hadith Gradingالألبانی:حسن صحيح | زبیر علی زئی:صحيح مسلم