“Whoever fasts six days after the Fitr will have completed the year, for whoever does a good deed will have the reward of ten like it.”  

عَنْ ثَوْبَانَ مَوْلَى رَسُولِ اللَّهِ ﷺ عَنْ رَسُولِ اللَّهِ ﷺ أَنَّهُ قَالَ مَنْ صَامَ سِتَّةَ أَيَّامٍ بَعْدَ الْفِطْرِ كَانَ تَمَامَ السَّنَةِ {مَنْ جَاءَ بِالْحَسَنَةِ فَلَهُ عَشْرُ أَمْثَالِهَا}  

“Whoever fasts Ramadan then follows it with six days of Shawwal, it is as if he fasted for a lifetime.”  

قَالَ رَسُولُ اللَّهِ ﷺ مَنْ صَامَ رَمَضَانَ ثُمَّ أَتْبَعَهُ بِسِتٍّ مِنْ شَوَّالٍ كَانَ كَصَوْمِ الدَّهْرِ