Messenger of Allah ﷺ entered upon me and said, "Have I not been informed that you offer prayer all the night and fast the whole day?" I said, "Yes." He said, "Do not do so; Offer prayer at night and also sleep; Fast for a few days and give up fasting for a few days because your body has a right on you, and your eye has a right on you, and your guest has a right on you, and your wife has a right on you. I hope that you will have a long life, and it is sufficient for you to fast for three days a month as the reward of a good deed, is multiplied ten times, that means, as if you fasted the whole year." I insisted (on fasting more) so I was given a hard instruction. I said, "I can do more than that (fasting)" The Prophet said, "Fast three days every week." But as I insisted (on fasting more) so I was burdened. I said, "I can fast more than that." The Prophet ﷺ said, "Fast as Allah's prophet David used to fast." I said, "How was the fasting of the prophet David?" The Prophet ﷺ said, "One half of a year (i.e. he used to fast on alternate days). ' (Using translation from Bukhārī 6134)   

دَخَلَ عَلَيَّ رَسُولُ اللهِ ﷺ فَقَالَ «أَلَمْ أُنَبَّأْ أَنَّكَ تَقُومُ اللَّيْلَ وَتَصُومُ النَّهَارَ؟» قَالَ بَلَى قَالَ «فَلَا تَفْعَلْ قُمْ وَنَمْ وَصُمْ وَأَفْطِرْ فَإِنَّ لِجَسَدِكَ عَلَيْكَ حَقًّا وَإِنَّ لِعَيْنِكَ عَلَيْكَ حَقًّا وَإِنَّ لِزَوْرِكَ عَلَيْكَ حَقًّا وَإِنَّ لِزَوْجَتِكَ عَلَيْكَ حَقًّا وَإِنَّ مِنْ حَسْبِكَ أَنْ تَصُومَ مِنْ كُلِّ شَهْرٍ ثَلَاثَةَ أَيَّامٍ فَإِنَّ لَكَ بِكُلِّ حَسَنَةٍ عَشْرَ أَمْثَالِهَا» فَشَدَّدْتُ فَشُدِّدَ عَلَيَّ قُلْتُ إِنِّي أُطِيقُ غَيْرَ ذَا قَالَ «فَصُمْ مِنْ كُلِّ جُمُعَةٍ ثَلَاثَةَ أَيَّامٍ» فَشَدَّدْتُ فَشُدِّدَ عَلَيَّ قُلْتُ إِنِّي أُطِيقُ غَيْرَ ذَا قَالَ «فَصُمْ صَوْمَ نَبِيِّ اللهِ دَاوُدَ» قُلْتُ وَمَا صَوْمُ نَبِيِّ اللهِ دَاوُدَ؟ قَالَ «نِصْفُ الدَّهْرِ»