Hadith
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنْ عَمْرِو بْنِ دِينَارٍ، عَنْ عَمْرِو بْنِ أَوْسٍ، أَنَّهُ سَمِعَ عَبْدَ اللَّهِ بْنَ عَمْرِو بْنِ الْعَاصِ، يَقُولُ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " أَحَبُّ الصِّيَامِ إِلَى اللَّهِ عَزَّ وَجَلَّ صِيَامُ دَاوُدَ عَلَيْهِ السَّلاَمُ كَانَ يَصُومُ يَوْمًا وَيُفْطِرُ يَوْمًا وَأَحَبُّ الصَّلاَةِ إِلَى اللَّهِ صَلاَةُ دَاوُدَ كَانَ يَنَامُ نِصْفَ اللَّيْلِ وَيَقُومُ ثُلُثَهُ وَيَنَامُ سُدُسَهُ " .
It was narrated from 'Amr bin Aws that he heard Abdullah bin Amr bin Al-'As say:"The Messenger of Allah (ﷺ) said: 'The most beloved of fasting to Allah is the fasting of Dawud, peace be upon him. He used to fast one day and not the next. And the most beloved of prayer to Allah (SWT) is the prayer of Dawud. He used to sleep half the night, spend one-third of the night in prayer and sleep for one-sixth of it
Sahih · Abu Ghuddah
Sunan an-Nasa'i 1630 ·Book 20, Hadith 33·Also available on sunnah.com·