Hadith 504910
Chapter 15: The Qur'an - كتاب القرآن
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ حُمَيْدِ بْنِ عَبْدِ الرَّحْمَنِ بْنِ عَوْفٍ، أَنَّهُ أَخْبَرَهُ أَنَّ {قُلْ هُوَ اللَّهُ أَحَدٌ} تَعْدِلُ ثُلُثَ الْقُرْآنِ وَأَنَّ {تَبَارَكَ الَّذِي بِيَدِهِ الْمُلْكُ} تُجَادِلُ عَنْ صَاحِبِهَا .
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.
Reference Muwatta Malik 504910
USC-MSA web (English) reference : Book 15, Hadith 19