From Sahih Muslim (Hadith 4623):
The tradition has been narrated by a different chain of transmitters with the following additions:(i) Then be (the Messenger of Allah) said with his hands one upon the other: Kill them (who stand in your way).... (ii) They (the Ansar) replied: We said so, Messenger of Allah! He said: What is my name? I am but Allah's bondman and His Messenger
Reference: Muslim 4623