Musnad Ahmad 603:1

Abdullah ibn Yazid narrated to us, Sa’id—meaning Ibn Abi Ayyub—narrated to us, Abu ‘Aqil Zuhrah ibn Ma’bad al-Taymi narrated to me, from his grandfather ‘Abdullah ibn Hisham, who had met the Prophet, may Allah bless him and grant him peace. His mother, Zaynab bint Humayd, took him to the Messenger of Allah, may Allah bless him and grant him peace, and said: "O Messenger of Allah, accept his pledge of allegiance." The Prophet, may Allah bless him and grant him peace, said: "He is young." He wiped his head and prayed for him. He used to sacrifice a single sheep on behalf of all his family members.