(39) باب اسْتِحْبَابِ صَوْمِ سِتَّةِ أَيَّامٍ مِنْ شَوَّالٍ اتِّبَاعًا لِرَمَضَانَ
Abu Ayyub al-Ansari (Allah be pleased with him) reported Allah's Messenger (ﷺ) as saying:
He who observed the fast of Ramadan and then followed it with six (fasts) of Shawwal. it would be as if he fasted perpetually. (ID)
Reference (ID): Sahih Muslim 1164 a (ID)
In-book reference (ID): Book 13, Hadith 264 (ID)
USC-MSA web (English) reference(deprecated numbering scheme): Book 6, Hadith 2614 (ID)