Sahih Bukhari Volume 4, Book 60, Hadith 3421

حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا سُفْيَانُ، عَنْ عَمْرِو بْنِ دِينَارٍ، عَنْ عَمْرِو بْنِ أَوْسٍ الثَّقَفِيِّ، سَمِعَ عَبْدَ اللَّهِ بْنَ عَمْرٍو، قَالَ قَالَ لِي رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ أَحَبُّ الصِّيَامِ إِلَى اللَّهِ صِيَامُ دَاوُدَ، كَانَ يَصُومُ يَوْمًا وَيُفْطِرُ يَوْمًا، وَأَحَبُّ الصَّلاَةِ إِلَى اللَّهِ صَلاَةُ دَاوُدَ، كَانَ يَنَامُ نِصْفَ اللَّيْلِ وَيَقُومُ ثُلُثَهُ وَيَنَامُ سُدُسَهُ ‏"‏‏.‏

Narrated By Abdullah bin Amr : Allah's Apostle said to me, "The most beloved fasting to Allah was the fasting of (the Prophet) David who used to fast on alternate days. And the most beloved prayer to Allah was the prayer of David who used to sleep for (the first) half of the night and pray for 1/3 of it and (again) sleep for a sixth of it."