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