Musannaf Ibn Abi Shayba 16:24

Abu Bakr narrated to us, he said: Muhammad ibn Bishr narrated to us, from Sa’id, from Qatadah, from al-Hasan, from Samurah, from the Prophet of Allah, may Allah bless him and grant him peace, who said: "An animal is slaughtered on his behalf on the seventh day, his head is shaved, and he is named."