أَخْبَرَنَا قُتَيْبَةُ، عَنْ مَالِكٍ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ عَبْدِ اللَّهِ بْنِ عَبْدِ الرَّحْمَنِ بْنِ أَبِي صَعْصَعَةَ، عَنْ أَبِيهِ، عَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ، أَنَّ رَجُلاً، سَمِعَ رَجُلاً، يَقْرَأُ ‏{‏ قُلْ هُوَ اللَّهُ أَحَدٌ ‏}‏ يُرَدِّدُهَا فَلَمَّا أَصْبَحَ جَاءَ إِلَى النَّبِيِّ صلى الله عليه وسلم فَذَكَرَ ذَلِكَ لَهُ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ وَالَّذِي نَفْسِي بِيَدِهِ إِنَّهَا لَتَعْدِلُ ثُلُثَ الْقُرْآنِ ‏"‏ ‏.‏

It was narrated from Abu Sa'eed Al Khudri that: A man heard another man reciting "Say: He is Allah, (the) One" and repeating it. When morning came he went to the Messenger of Allah (PBUH) and told him about that. The Messenger of Allah (PBUH) said: "By the One in Whose Hand is my soul, it is equal to one-third of the Quran." Translation Not Available

Book Ref: Sunan An Nisai Book 11 Hadith 995
Web Ref:  Sunan An Nisai Vol 2 Book 11 Hadith 996