Translation
(97) Oneness, Uniqueness of Allah (Tawheed)
كتاب التوحيد
(13) Chapter: Asking Allah with His Names and seeking refuge with them
(13) باب السُّؤَالِ بِأَسْمَاءِ اللَّهِ تَعَالَى، وَالاِسْتِعَاذَةِ بِهَا
Sahih al-Bukhari 7399 

Narrated Anas:

The Prophet (ﷺ) slaughtered two rams as sacrifice and mentioned Allah's Name and said, "Allahu-Akbar" while slaughtering).

حَدَّثَنَا حَفْصُ بْنُ عُمَرَ، حَدَّثَنَا هِشَامٌ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ، قَالَ ضَحَّى النَّبِيُّ صلى الله عليه وسلم بِكَبْشَيْنِ، يُسَمِّي وَيُكَبِّرُ‏.‏
Reference : Sahih al-Bukhari 7399
In-book reference : Book 97, Hadith 28
USC-MSA web (English) reference : Vol. 9, Book 93, Hadith 496
  (deprecated numbering scheme)