Sahih Bukhari, Hadith: Q5013, (13) Chapter. The superiority of Qul-Huwa Allahu Ahad. ["Say (O Muhammad ): He is Allah, (the) One."] (i.e., Surat Al-Iklas) [No.112].

صحيح البخاري

Sahih Bukhari

كتاب فضائل القرآن

The Book of The Virtues of The Quran

باب فضل قل هو الله أحد:

(13) Chapter. The superiority of Qul-Huwa Allahu Ahad. ["Say (O Muhammad): He is Allah, (the) One."] (i.e., Surat Al-Iklas) [No.112].