Yahya related to me from Malik from Ibn Shihab that Humayd ibnAbd ar-Rahman ibn Awf had told him that Surat al-Ikhlas (Sura 112) wasequal to a third of the Qur'an, and that Surat al-Mulk (Sura 67)pleaded for its owner.
USC-MSA web (English) reference: Book 15, Hadith 19
Arabic reference: Book 15, Hadith 491