كتاب الأضاحي
Read the English translation first, with the original Arabic directly underneath.
Narrated Anas:
The Prophet (ﷺ) slaughtered two rams, black and white in color (as sacrifices), and I saw him putting his foot on their sides and mentioning Allah's Name and Takbir (Allahu Akbar). Then he slaughtered them with his own hands.
حَدَّثَنَا آدَمُ بْنُ أَبِي إِيَاسٍ، حَدَّثَنَا شُعْبَةُ، حَدَّثَنَا قَتَادَةُ، عَنْ أَنَسٍ، قَالَ ضَحَّى النَّبِيُّ صلى الله عليه وسلم بِكَبْشَيْنِ أَمْلَحَيْنِ، فَرَأَيْتُهُ وَاضِعًا قَدَمَهُ عَلَى صِفَاحِهِمَا يُسَمِّي وَيُكَبِّرُ، فَذَبَحَهُمَا بِيَدِهِ.