Al-Bukhari reported in his Sahih that Abu Said Al-Khudri, may Allah be pleased with him, narrated that the Prophet (Sallallahu Alaihi wa Sallam) told the companions: “Are you not able to read a third of the Qur'an in one night?” They found this very difficult and replied that nobody amongst us can do so. Then the Prophet (Sallallahu Alaihi wa Sallam) said: “Allah, The One, the Self sufficient "Surah Qul Huwa Allahu Ahad equals a third of the Qur'an.”

Muslim also reported that Abu Al Darda narrated: “Say, He is Allah, The One, (Surah 112) equals a third of the Qur'an.” reported by Al-Thirmidhi, and Al- Albani classified it as an authentic Hadith.

Al-Mubarakpuri stated in Sharh Al-Thirmidhi that it could mean that whoever reads it 3 times is as if he reads the whole Qur'an.

390 The Quran 16:18 (Surah an-Nahl)

“And if you should count the favors of Allah, you could not enumerate them. Indeed, Allah is Forgiving and Merciful.”