Abu Dawud
Prayer
Book Number: 002 / Hadith Number: 426
Narated By Umm Farwah : The Apostle of Allah (pbuh) 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 (pbuh): He was questioned.