Narrated Abu Said Al-Khudri:
A man heard another man reciting (Surat-Al-Ikhlas) ‘Say He is Allah, (the) One.’ (112. 1) repeatedly. The next morning he came to Allah’s Apostle and informed him about it as if he thought that it was not enough to recite. On that Allah’s Apostle said, “By Him in Whose Hand my life is, this Surah is equal to one-third of the Qur’an!”