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.  

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