Prayer (Kitab Al-Salat)
Dawud :: Book 2 : Hadith 426
Narrated Umm Farwah:
The Apostle of Allah (peace_be_upon_him) was asked: Which of the actions is best? He replied: Observing prayer early in its period.
Al-Khuza'i narrated in his version from his aunt named Umm Farwah who took the oath of allegiance to the Prophet (peace_be_upon_him): He was questioned.