From Sahih Bukhari (Hadith 3420):
Narrated `Abdullah bin `Amr:Allah's Messenger (ﷺ) 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
Reference: Bukhari 3420