Sunan an-Nasa'i, Hadith 4417 ⓘ
It was narrated that Anas said: "I saw him: - meaning the Prophet - "slaughtering them with his own hand, and placing his foot on their sides, pronouncing the name of Allah and saying: 'Allah Akbar,' (sacrificing) two horned, Amlah rams." (Sahih )
أَخْبَرَنَا الْقَاسِمُ بْنُ زَكَرِيَّا بْنِ دِينَارٍ، قَالَ حَدَّثَنَا مُصْعَبُ بْنُ الْمِقْدَامِ، عَنِ الْحَسَنِ، - يَعْنِي ابْنَ صَالِحٍ - عَنْ شُعْبَةَ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ، قَالَ لَقَدْ رَأَيْتُهُ - يَعْنِي النَّبِيَّ صلى الله عليه وسلم - يَذْبَحُهُمَا بِيَدِهِ وَاضِعًا عَلَى صِفَاحِهِمَا قَدَمَهُ يُسَمِّي وَيُكَبِّرُ كَبْشَيْنِ أَمْلَحَيْنِ أَقْرَنَيْنِ .
also referenced under: Book 43, Hadith 57 (In-Book) & Volume 5, Book 43, Hadith 4422 (DarusSalam)