Al-Adab Al-Mufrad #963

He also said, "One of the slaves of the Ansar had a son whom he named Muhammad, The Ansar said, 'We will not give you the kunya of the Messenger of Allah until we have sat in the road and asked the Prophet about the Final Hour.' The Prophet said, 'You have come to me to ask me about the Hour?' 'Yes,' we replied. He said, 'There is no one alive now who will see it, even if he lives a hundred years.' We said, 'A slave of the Ansar has had a son and named him Muhammad. The Ansar said, "We will not call you by the kunya of the Messenger of Allah."' The Prophet said, 'You have done well. Call yourselves with my name, but do not use my kunya.'"