While the Prophet (ﷺ) was in the market, somebody, called, "O Abul-Qasim." The Prophet (ﷺ) turned to him.The man said, "I have called to this (i.e. another man)." The Prophet (ﷺ) said, "Name yourselves by myname but not by my Kunya (name)." (In Arabic world it is the custom to call the man as the father ofhis eldest son, e.g. Abul-Qasim.)