Sahih Muslim Book 5, Hadith Number 2302.
Chapter : Bestowal upon those who are made to incline (to truth).
This Hadith has been narrated on the authority of Muhammad b. Sa’d through another chain of transmitters (and the words are): “The Messenger of Allah (may peace be upon him) struck between my neck and shoulder with his hand and said: Do you wrangle, O Sa’d, because I bestow (some gifts) upon a person?”