Bukhari 2120

From Sahih Bukhari (Hadith 2120):

Narrated Anas bin Malik: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 my name but not by my Kunya (name)." (In Arabic world it is the custom to call the man as the father of his eldest son, e.g. Abul-Qasim.) (See Hadith No. 737, Vol)