Sahih Bukhari Volume 004, Book 055, Hadith Number 628.
Narated By Abu Huraira : The Prophet said, "The reciting of the Zabur (i.e. Psalms) was made easy for David. He used to order that his riding animals be saddled, and would finish reciting the Zabur before they were saddled. And he would never eat except from the earnings of his manual work."