Qatada bin Numan reported,

He said that a man stood in prayer during the time of the Prophet ﷺ and in the hours before dawn recited "Say, He is Allah, the One" [Ikhlas 112:1], repeating it over and over and adding nothing to it. When morning came, a man went to the Prophet ﷺ and said, "Messenger of Allah, so-and-so stood in prayer last night and before dawn he recited 'Say, He is Allah, the One. Allah, the Eternal Refuge. He neither begets nor is born, and there is none comparable to Him' [Ikhlas 112:1–4], repeating it over and over and adding nothing to it." It was as though the man thought little of it.The Prophet ﷺ said, "By Him in whose hand is my soul, it equals a third of the Quran."

Azami 13802

Sahih

عن قتادة بن النعمان

قال إن رجلا قام في زمن النبي ﷺ يقرأ من السحر: {قل هو الله أحد} يرددها لا يزيد عليها، فلما أصبح أتى رجل النبي ﷺ فقال: يا رسول الله إن فلانا قام الليلة، فقرأ في السحر: {قل هو الله أحد الله الصمد لم يلد ولم يولد ولم يكن له كفوا أحد} يرددها لا يزيد عليها كأن الرجل يتقالها- قال النبي ﷺ والذي نفسي بيده إنها لتعدل ثلث القرآن.

الأعظمي 13802صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Tafsir of the great Quran
Chapter
Tafsir of Surah Ikhlas
Section
His saying, "Say: He is Allah, the One. Allah, the Eternal Refuge. He neither begets nor is begotten"
Numbering
Jami al-Kamil 13802 (2nd edition)
Azami 13802