Sunan Ibn Majah 3787
سنن ابن ماجه#3787SahihIt was narrated that Abu Hurairah said that the Messenger of Allah(ﷺ) said:"Qul Huwa Allahu ahad [Say: He is Allah, (the) One] is equivalent to one third of the Quran
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Fouad Abd al-BaqiSahih
Shuaib Al ArnautHasan Sahih
Zubair Ali ZaiIsnaad Sahih
In-book reference: 33:131