"I asked Aishah about the Prophet's fasting.' She said: 'He would fast until we said: "He has fasted" and he would abstain from fasting until we said: "He has abstained from fasting." (She said:) 'The Messenger of Allah did not fast an entire month except Ramadan.'"  

عَنْ صِيَامِ النَّبِيِّ ﷺ قَالَتْ كَانَ يَصُومُ حَتَّى نَقُولَ قَدْ صَامَ وَيُفْطِرُ حَتَّى نَقُولَ قَدْ أَفْطَرَ قَالَتْ وَمَا صَامَ رَسُولُ اللَّهُ ﷺ شَهْرًا كَامِلاً إِلاَّ رَمَضَانَ وَفِي الْبَابِ عَنْ أَنَسٍ وَابْنِ عَبَّاسٍ  

Anas bin Malik was asked about the Prophet's fasting and he said: "He would fast during a month until we thought that he did not want to abstain from fasting during any of it. And, he would not fast during a month until we thought that he did not want to fast during any of it. (There was no time) that I wanted to see if he was performing Salat during the night, except that I would see him praying, nor to see him sleeping, except that I would see him sleeping."  

عَنْ صَوْمِ النَّبِيِّ ﷺ قَالَ كَانَ يَصُومُ مِنَ الشَّهْرِ حَتَّى نَرَى أَنَّهُ لاَ يُرِيدُ أَنْ يُفْطِرَ مِنْهُ وَيُفْطِرُ حَتَّى نَرَى أَنَّهُ لاَ يُرِيدُ أَنْ يَصُومَ مِنْهُ شَيْئًا وَكُنْتَ لاَ تَشَاءُ أَنْ تَرَاهُ مِنَ اللَّيْلِ مُصَلِّيًا إِلاَّ رَأَيْتَهُ مُصَلِّيًا وَلاَ نَائِمًا إِلاَّ رَأَيْتَهُ نَائِمًا  

The Messenger of Allah said: "The most virtuous fast is the fast of my brother Dawud. He would fast a day, and not fast (the next) day. He would not flee at the time of engagement (with the enemy)."  

قَالَ رَسُولُ اللَّهِ ﷺ أَفْضَلُ الصَّوْمِ صَوْمُ أَخِي دَاوُدَ كَانَ يَصُومُ يَوْمًا وَيُفْطِرُ يَوْمًا وَلاَ يَفِرُّ إِذَا لاَقَى