Imam Ali (AS) has said:

"Learn the Quran for it is the best of the discourses, and understand it thoroughly for it is the best blossoming of the hearts.  Seek cure with its light for it is the cure of the hearts.  Recite it beautifully for it is the most beneficial of the  narrations."

Nahjul Balaghah
Sermon 110 (109 in some books)