قَالَ رَسُولُ اللهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ: مَنْ صَامَ رَمَضَانَ وَأَتْبَعَهُ سِتًّا مِنْ شَوَّالٍ خَرَجَ مِنْ ذُنُوبِهِ كَيَوْمِ وَلَدَتْهُ أُمُّهُ. (طس)
Rasûlullâh Sallallâhu Alayhi Wa Sallam said: “Whoever fasts in the Month of Ramadhân and follows it with six (more) days in Shawwâl will be purified from his sins as on the day he was born (from his mother).” (Tabarânî, Al-Mu’jam Al-Awsat)
Shawwal is the first month of Hajj. Eid Al-Fitr (Festival day after Ramadhân) is the first day of Shawwal in which Muslims are recommended to recite Salawât (durud) upon Nabi Sallâllahu Alayhi Wa Sallam.
Muslims are advised to keep (nafil) fast for six days in this month. If one starts fasting from 12th day to the 17th of this month, then the days of “Ayyam Al-Bidh” (13, 14 and 15 of each month) are also covered which will be an extra rewarding practice.
Rasûlullâh Sallâllahu Alayhi Wa Sallam gave the good news that those who fast six days in the month of Shawwal will be regarded and rewarded as if they fasted for the whole year. (Du‘as [Invocations] and ‘Ibâdahs [Acts of Worship])