Sunan Abi Dawud, Hadith 2442

'Abd Allah b. 'And (b. al-'As) said: The Messenger of Allah said to me: The fast most liked by Allah is the one observed by Dawud (David), and the prayer dearer to Allah is the one offered by Dawud (David): he would sleep half the night, and stand (in prayer) one-third of it, and sleep one-sixth of it. He would go without fasting one day, and fast the other day.

حَدَّثَنَا أَحْمَدُ بْنُ حَنْبَلٍ، وَمُحَمَّدُ بْنُ عِيسَى، وَمُسَدَّدٌ، - وَالإِخْبَارُ فِي حَدِيثِ أَحْمَدَ - قَالُوا حَدَّثَنَا سُفْيَانُ قَالَ سَمِعْتُ عَمْرًا قَالَ أَخْبَرَنِي عَمْرُو بْنُ أَوْسٍ سَمِعَهُ مِنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو قَالَ قَالَ لِي رَسُولُ اللَّهِ صلى الله عليه وسلم ‏ "‏ أَحَبُّ الصِّيَامِ إِلَى اللَّهِ تَعَالَى صِيَامُ دَاوُدَ وَأَحَبُّ الصَّلاَةِ إِلَى اللَّهِ صَلاَةُ دَاوُدَ كَانَ يَنَامُ نِصْفَهُ وَيَقُومُ ثُلُثَهُ وَيَنَامُ سُدُسَهُ وَكَانَ يُفْطِرُ يَوْمًا وَيَصُومُ يَوْمًا ‏" ‏ ‏.‏

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also referenced under: Hadith 2448 (DarusSalam)