"I entered with Zaid upon 'Abdullah bin Amr and he narrated: 'The Messenger of Allah was told about my fasting, so the entered upon me and I gave him an average-sized leather pillow that was stuffed with palm fibvers. He sat in the ground with the pillow between myself and him, and said: "Whill it not be sufficient for you to fast three days each months?" I said: O Messenger of Allah! He said: "O Messenger of Allah!" He said: "Eleven." I said: "O Messenger of Allah!" Then the Prophet said: "There is not fast better than the fast of Dawud, half of a lifetime, fasting one day and not next." (Using translation from Nasāʾī 2402)  

أَنَّ رَسُولَ اللهِ ﷺ ذُكِرَ لَهُ صَوْمِي فَدَخَلَ عَلَيَّ قَالَ فَأَلْقَيْتُ لَهُ وِسَادَةً حَشْوُهَا لِيفٌ فَجَلَسَ عَلَى الْأَرْضِ فَصَارَتِ الْوِسَادَةُ فِيمَا بَيْنِي وَبَيْنَهُ فَقَالَ «أَمَا يَكْفِيكَ مِنْ كُلِّ شَهْرٍ ثَلَاثَةَ أَيَّامٍ؟» قُلْتُ زِدْنِي يَا رَسُولَ اللهِ قَالَ «خَمْسًا» قُلْتُ يَا رَسُولَ اللهِ قَالَ «سَبْعًا» قُلْتُ يَا رَسُولَ اللهِ قَالَ «تِسْعًا» قُلْتُ يَا رَسُولَ اللهِ قَالَ «أحْدَ عَشَرَ»؟ قُلْتُ يَا رَسُولَ اللهِ قَالَ النَّبِيُّ ﷺ «لَا صَوْمَ فَوْقَ صَوْمِ دَاوُدَ شَطْرَ الدَّهْرِ صِيَامُ يَوْمٍ وَفِطْرُ يَوْمٍ»