Sahih al-Bukhari Book 34, Hadith 74
A man at Al-Baqi' called, "O Abul-Qasim!" The Prophet (ﷺ) turned to him and the man said (to the
Prophet ), "I did not intend to call you." The prophet said, "Name yourselves by my name but not by
my Kunya (name).
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. 4)
Once the Prophet (ﷺ) went out during the day. Neither did he talk to me nor I to him till he reached the market of Bani Qainuqa and then he sat in the compound of Fatima's house and asked about the small boy (his grandson Al-Hasan) but Fatima kept the boy in for a while. I thought she was either changing his clothes or giving the boy a bath. After a while the boy came out running and the Prophet (ﷺ) embraced and kissed him and then said, 'O Allah! Love him, and love whoever loves him.'