Sayyidah Aishah (may Allah be pleased with her) said that the Messenger of Allah (peace and blessings be upon him) ordered that a horned ram with black legs, black eyes and a black belly be sacrificed, and said: "O Aishah, bring the knife." Then he said: "Sharpen it on a stone." When she had sharpened the knife, he (peace and blessings be upon him) took hold of a ram and slaughtered it, and said: 'Bismillah, Allahumma taqabbal min Muhammadin wa ali Muhammadin wa min ummati Muhammad' (In the name of Allah. O Allah, accept (it) on behalf of Muhammad (peace and blessings be upon him), the family of Muhammad and the Ummah of Muhammad). Then he (peace and blessings be upon him) offered the sacrifice.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19046