Maliks Muwatta Book 15, Hadith Number 19.
Section : About Reciting Surat al-Ikhlas and Surat al-Mulk.
Yahya related to me from Malik from Ibn Shihab that Humayd ibn Abd ar-Rahman ibn Awf had told him that Surat al-Ikhlas (Sura 112) was equal to a third of the Qur’an, and that Surat al-Mulk (Sura 67) pleaded for its owner.