Musnad Ahmad 652:36

Sufyan ibn 'Uyaynah narrated to us, al-Zuhri narrated to us, from Muhammad ibn al-Nu'man ibn Bashir and Humayd ibn 'Abd al-Rahman ibn 'Awf, that they informed him that they heard al-Nu'man ibn Bashir saying: My father gave me a gift of a slave. So I came to the Messenger of Allah, peace and blessings of Allah be upon him, to have him witness it. He said: "Have you given all of your children a gift like this?" He said: "No." He said: "Then take it back."