It is narrated from Sayyiduna Anas bin Malik that the Messenger of Allah used to slaughter two beautiful, spotted, horned rams and would recite « بِسْمِاللهِ ، اللهُأَكْبَرُ ». I saw him slaughtering them with his own blessed hand; he had his foot placed on their side.
Hadith Referenceصحيح ابن خزيمه / جماع أبواب ذكر أفعال اختلف الناس فى إباحته للمحرم، نصت سنة النبى صلى الله عليه وسلم أو دلت على إباحتها / 2895