Narrated Abu Hurairah:
that the Messenger of Allah (ﷺ) said: "Qul Huwa Allahu Ahad is equal to a third of the Qur'an." (RU)
English reference (RU): Vol. 5, Book 42, Hadith 2899 (RU)
Arabic reference (RU): Book 45, Hadith 3145 (RU)