Sayyiduna Abdullah bin Amr bin al-As (may Allah be pleased with them both) says that the Messenger of Allah (peace and blessings be upon him) said to me: "The most beloved fasting to Allah is the fasting of Dawud (peace be upon him); he would fast one day and break his fast one day. And the most beloved prayer to Allah is the prayer of Dawud (peace be upon him), for he would first sleep half the night, then stand in prayer for a third of it, then sleep for a sixth of it."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4656