صحيح البخاري Sahih Bukhari كتاب الأضاحي The Book of Al-Adahi
بَابُ التَّكْبِيرِ عِنْدَ الذَّبْحِ:

(14) Chapter. To say Takbir (Allahu Akbar) while slaughtering (a sacrifice).

1 hadith
Hadith 5565
حَدَّثَنَا قُتَيْبَةُ ، حَدَّثَنَا أَبُو عَوَانَةَ ، عَنْ قَتَادَةَ ، عَنْ أَنَسٍ ، قَالَ : " ضَحَّى النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ بِكَبْشَيْنِ أَمْلَحَيْنِ أَقْرَنَيْنِ ذَبَحَهُمَا بِيَدِهِ وَسَمَّى ، وَكَبَّرَ ، وَوَضَعَ رِجْلَهُ عَلَى صِفَاحِهِمَا " .
Narrated Anas: The Prophet offered as sacrifices, two horned rams, black and white in color. He slaughtered them with his own hands and mentioned Allah's Name over them and said Takbir and put his foot on their sides.
Hadith Reference Sahih Bukhari / The Book of Al-Adahi / Hadith: 5565
Hadith Grading محدثین: أحاديث صحيح البخاريّ كلّها صحيحة