Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) narrates that the Messenger of Allah (peace and blessings be upon him) said: "The most beloved prayer to Allah Almighty is the prayer of Dawud (peace be upon him): he would sleep half the night, then stand (in prayer) for a third of it after its half, and then sleep its last part. And the most beloved fasting to Allah Almighty is the fasting of Dawud (peace be upon him): he would fast one day and not fast the next."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8450