AS REPORTED in a great number of authentic Traditions, the Prophet was wont to describe this surah as "equivalent to one-third of the whole Qur'an" (Bukhari, Muslim, Ibn Hanbal, Abu Da'ud, Nasa'i, Tirmidhi, Ibn Majah). It seems to have been revealed in the early part of the Mecca period.
SAY: "He is the One God: