كتاب الأضاحى
35  
The Book of Sacrifices
(3)
Chapter: It is recommended to select a good animal for the sacrifice and to slaughter it oneself, not delegating it to anyone else, and to say the name of Allah, and to say the Takbir
(3)
باب اسْتِحْبَابِ الضَّحِيَّةِ وَذَبْحِهَا مُبَاشَرَةً بِلاَ تَوْكِيلٍ وَالتَّسْمِيَةِ وَالتَّكْبِيرِ ‏‏
Sahih Muslim 1966 a

Anas reported that Allah's Messenger (ﷺ) sacrificed with his own hands two horned rams which were white with black markings reciting the name of Allah and glorifying Him (saying Allah-o-Akbar). He placed his foot on their sides (while sacrificing).

حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا أَبُو عَوَانَةَ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ، قَالَ ضَحَّى النَّبِيُّ صلى الله عليه وسلم بِكَبْشَيْنِ أَمْلَحَيْنِ أَقْرَنَيْنِ ذَبَحَهُمَا بِيَدِهِ وَسَمَّى وَكَبَّرَ وَوَضَعَ رِجْلَهُ عَلَى صِفَاحِهِمَا ‏.‏
Reference : Sahih Muslim 1966a
In-book reference : Book 35, Hadith 24
USC-MSA web (English) reference : Book 22, Hadith 4841
  (deprecated numbering scheme)