´Jubair narrated from Abu Ad-Darda, or Abu Dharr, that :` Allah's Messenger narrated that Allah, Blessed and Most High said: "Son of Adam: Perform four Rak'ah for Me in the beginning of the day it will suffice you for the latter part of it."
Hadith ReferenceSunan at-Tirmidhi / The Book on Al-Witr / Hadith: 475