question #3 Sahih al-Bukhari 4059, Book 64, Hadith 105 : What can be inferred about the relationship between the Prophet Muhammad (ﷺ) and Sa’d bin Malik from this statement?

I have never heard the Prophet (ﷺ) mentioning his father and mother for anybody other than Sa`d bin
Malik. I heard him saying on the day of Uhud, “O Sa`d throw (arrows)! Let my father and mother be
sacrificed for you !”