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