The Book of the Commencement of the Prayer
11/39. Chapter:
Reciting: "Say: O you disbelievers" and "Say: He is Allah, (the) One" in the two rak'ahs
Sunan an-Nasai
أَخْبَرَنَا عَبْدُ الرَّحْمَنِ بْنُ إِبْرَاهِيمَ، دُحَيْمٌ قَالَ حَدَّثَنَا مَرْوَانُ، قَالَ حَدَّثَنَا يَزِيدُ بْنُ كَيْسَانَ، عَنْ أَبِي حَازِمٍ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَرَأَ فِي رَكْعَتَىِ الْفَجْرِ { قُلْ يَا أَيُّهَا الْكَافِرُونَ } وَ { قُلْ هُوَ اللَّهُ أَحَدٌ }
It was narrated from Abu Hurairah that: The Messenger of Allah (ﷺ) recited: "Say: O you disbelievers" and "Say: He is Allah, (the) One" in the two rak'ahs of Fajr.
Reference : Sunan an-Nasa'i 945In-book reference : Book 11, Hadith 70English translation : Vol. 2, Book 11, Hadith 946