It was narrated that Abu Qatadah said:
“Umar bin Khattab said: ‘O Messenger of Allah! What about a person who fasts two days and does not fast one day?’ He said: ‘Is anyone able to do that?’ He said: ‘O Messenger of Allah! What about a person who fasts one day and not the next?’ He said: ‘That is the fast of Dawud.’ He said: ‘What about a man who fasts one day and does not fast the next two days?’ He said: ‘I wish that I were given the ability to do that.’”

حَدَّثَنَا أَحْمَدُ بْنُ عَبْدَةَ، حَدَّثَنَا حَمَّادُ بْنُ زَيْدٍ، حَدَّثَنَا غَيْلاَنُ بْنُ جَرِيرٍ، عَنْ عَبْدِ اللَّهِ بْنِ مَعْبَدٍ الزِّمَّانِيِّ، عَنْ أَبِي قَتَادَةَ، قَالَ قَالَ عُمَرُ بْنُ الْخَطَّابِ يَا رَسُولَ اللَّهِ كَيْفَ بِمَنْ يَصُومُ يَوْمَيْنِ وَيُفْطِرُ يَوْمًا قَالَ " وَيُطِيقُ ذَلِكَ أَحَدٌ " . قَالَ يَا رَسُولَ اللَّهِ كَيْفَ بِمَنْ يَصُومُ يَوْمًا وَيُفْطِرُ يَوْمًا قَالَ " ذَلِكَ صَوْمُ دَاوُدَ " . قَالَ كَيْفَ بِمَنْ يَصُومُ يَوْمًا وَيُفْطِرُ يَوْمَيْنِ قَالَ " وَدِدْتُ أَنِّي طُوِّقْتُ ذَلِكَ " .