Musnad Ahmad 33:846

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, from Husayn, from Salim ibn Abi al-Ja'd, from Jabir ibn Abdullah, who said: A boy was born to a man from the Ansar, and he wanted to name him Muhammad. So he went with him to the Messenger of Allah, may Allah bless him and grant him peace, and they asked him. He said: "Name yourselves with my name, but do not use my kunya (patronymic), for I have been sent as a distributor (qasim) to distribute among you."