Narrated `Abdullah bin `Amr:Allah's Messenger (ﷺ) was informed about my fasts, and he came to me and I spread for him a leather cushion stuffed with palm fires, but he sat on the ground and the cushion remained between me and him, and then he said, "Isn't it sufficient for you to fast three days a month?" I replied, "O Allah's Apostle! (I can fast more)." He said, "Five?" I replied, "O Allah's Messenger (ﷺ)! (I can fast more)." He said, "Seven?" I replied, "O Allah's Messenger (ﷺ)! (I can fast more)." He said, "Nine (days per month)?" I replied, "O Allah's Messenger (ﷺ)! (I can fast more)" He said, "Eleven (days per month)?" And then the Prophet said, "There is no fast superior to that of the Prophet (ﷺ) David it was for half of the year. So, fast on alternate days."
حَدَّثَنَا إِسْحَاقُ الْوَاسِطِيُّ، حَدَّثَنَا خَالِدٌ، عَنْ خَالِدٍ، عَنْ أَبِي قِلاَبَةَ، قَالَ أَخْبَرَنِي أَبُو الْمَلِيحِ، قَالَ دَخَلْتُ مَعَ أَبِيكَ عَلَى عَبْدِ اللَّهِ بْنِ عَمْرٍو فَحَدَّثَنَا أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم ذُكِرَ لَهُ صَوْمِي فَدَخَلَ عَلَىَّ، فَأَلْقَيْتُ لَهُ وِسَادَةً مِنْ أَدَمٍ، حَشْوُهَا لِيفٌ، فَجَلَسَ عَلَى الأَرْضِ، وَصَارَتِ الْوِسَادَةُ بَيْنِي وَبَيْنَهُ. فَقَالَ " أَمَا يَكْفِيكَ مِنْ كُلِّ شَهْرٍ ثَلاَثَةُ أَيَّامٍ ". قَالَ قُلْتُ يَا رَسُولَ اللَّهِ. قَالَ " خَمْسًا ". قُلْتُ يَا رَسُولَ اللَّهِ. قَالَ " سَبْعًا ". قُلْتُ يَا رَسُولَ اللَّهِ. قَالَ " تِسْعًا ". قُلْتُ يَا رَسُولَ اللَّهِ. قَالَ " إِحْدَى عَشْرَةَ ". ثُمَّ قَالَ النَّبِيُّ صلى الله عليه وسلم " لاَ صَوْمَ فَوْقَ صَوْمِ دَاوُدَ ـ عَلَيْهِ السَّلاَمُ ـ شَطْرَ الدَّهْرِ، صُمْ يَوْمًا، وَأَفْطِرْ يَوْمًا ".
Bukhari
Fasting • Hadith 87