Abu Sa’id al-Khudri reported: A man heard another man reciting, “Say, He is Allah, the One,” (112:1) again and again. The next morning he came to the Messenger of Allah, peace and blessings be upon him, and told him about it, as if he thought it was not enough to recite. The Prophet said, “By the One in whose hand is my soul, it is equal to a third of the Quran.”
Source: Ṣaḥīḥ al-Bukhārī 5013
Grade: Sahih (authentic) according to Al-Bukhari
عَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ أَنَّ رَجُلًا سَمِعَ رَجُلًا يَقْرَأُ قُلْ هُوَ اللَّهُ أَحَدٌ يُرَدِّدُهَا فَلَمَّا أَصْبَحَ جَاءَ إِلَى رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَذَكَرَ ذَلِكَ لَهُ وَكَأَنَّ الرَّجُلَ يَتَقَالُّهَا فَقَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ وَالَّذِي نَفْسِي بِيَدِهِ إِنَّهَا لَتَعْدِلُ ثُلُثَ الْقُرْآنِ
5013 صحيح البخاري كتاب فضائل القرآن باب فضل قل هو الله أحد