Bulugh al-Maram
Book 12, Hadith 30
Arabic hadith text
وَفِي لَفْظٍ لِمُسْلِمٍ, وَيَقُولُ: { بِسْمِ اَللَّهِ. وَاَللَّهُ أَكْبَرُ } (1765) .4 - مسلم ( 1966 ) ( ج 3 / ص 1557 ).
Translation
In a version by Muslim, 'and would say Bismillah and Allahu Akbar.'