كتاب الصيام
13  
The Book of Fasting
(35)
Chapter: Prohibition of Fasting for a lifetime for the one who will be harmed by that or who will neglect other duties, or does not break his fast on the two 'Ids or during the days of At-Tashriq; It is better to fast alternate days
(35)
بَاب النَّهْيِ عَنْ صَوْمِ الدَّهْرِ لِمَنْ تَضَرَّرَ بِهِ أَوْ فَوَّتَ بِهِ حَقًّا أَوْ لَمْ يُفْطِرْ الْعِيدَيْنِ وَالتَّشْرِيقَ وَبَيَانِ تَفْضِيلِ صَوْمِ يَوْمٍ وَإِفْطَارِ يَوْمٍ
Sahih Muslim 1159 c

This hadith has been narrated by Yahya b. Abu Kathir with the same chain of transmitters and he made this addition after these words:

During every month, (fasting) for three days, there is for you ten times for every good and that is perpetual fasting (for three days would bring a reward for full thirty days). I said: What is the fast of the Messenger of Allah, David? He said: Half of the age (observing fast on alternate days for the whole life). And in the hadith no mention has been made of the recital of the Qur'an, and he did not say: Your visitor has a right upon you, but (instead) he said: Your son has a right upon you.
وَحَدَّثَنِيهِ زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا رَوْحُ بْنُ عُبَادَةَ، حَدَّثَنَا حُسَيْنٌ الْمُعَلِّمُ، عَنْ يَحْيَى، بْنِ أَبِي كَثِيرٍ بِهَذَا الإِسْنَادِ وَزَادَ فِيهِ بَعْدَ قَوْلِهِ ‏"‏ مِنْ كُلِّ شَهْرٍ ثَلاَثَةَ أَيَّامٍ ‏"‏ ‏"‏ فَإِنَّ لَكَ بِكُلِّ حَسَنَةٍ عَشْرَ أَمْثَالِهَا فَذَلِكَ الدَّهْرُ كُلُّهُ ‏"‏ ‏.‏ وَقَالَ فِي الْحَدِيثِ قُلْتُ وَمَا صَوْمُ نَبِيِّ اللَّهِ دَاوُدَ قَالَ ‏"‏ نِصْفُ الدَّهْرِ ‏"‏ ‏.‏ وَلَمْ يَذْكُرْ فِي الْحَدِيثِ مِنْ قِرَاءَةِ الْقُرْآنِ شَيْئًا وَلَمْ يَقُلْ ‏"‏ وَإِنَّ لِزَوْرِكَ عَلَيْكَ حَقًّا ‏"‏ ‏.‏ وَلَكِنْ قَالَ ‏"‏ وَإِنَّ لِوَلَدِكَ عَلَيْكَ حَقًّا ‏"‏ ‏.‏
Reference : Sahih Muslim 1159c
In-book reference : Book 13, Hadith 237
USC-MSA web (English) reference : Book 6, Hadith 2588
  (deprecated numbering scheme)