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 b

Anas reported that Allah's Messenger (ﷺ) sacrificed two horned rams of white colour with black markings over them. He also stated:

I saw him sacrificing them with his own hand and saw him placing his foot on their sides, and recited the name of Allah and Glorified Him.
حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، أَخْبَرَنَا وَكِيعٌ، عَنْ شُعْبَةَ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ، قَالَ ضَحَّى رَسُولُ اللَّهِ صلى الله عليه وسلم بِكَبْشَيْنِ أَمْلَحَيْنِ أَقْرَنَيْنِ قَالَ وَرَأَيْتُهُ يَذْبَحُهُمَا بِيَدِهِ وَرَأَيْتُهُ وَاضِعًا قَدَمَهُ عَلَى صِفَاحِهِمَا قَالَ وَسَمَّى وَكَبَّرَ ‏.‏
Reference : Sahih Muslim 1966b
In-book reference : Book 35, Hadith 25
USC-MSA web (English) reference : Book 22, Hadith 4842
  (deprecated numbering scheme)