Anas ibn Malik said, "The Prophet, may Allah bless him and grant
him peace, was in the market when a man said, 'Abu'l-Qasim!' The Prophet,
may Allah bless him and grant him peace, turned towards him. He said, 'Messenger
of Allah, I was calling this man.' The Prophet, may Allah bless him and
grant him peace, said, 'Call yourselves with my name but do no use my kunya.'"