Anas said: The Messenger of Allah (peace be upon him) was one of the best of men in character. One day he sent me to do something, and I said: I swore by Allah that I would not go. But in my heart I felt that I should go to do what the Prophet of Allah (peace be upon him) had commanded me; so I went out and came upon some boys who were playing in the street. All of a sudden the Messenger of Allah (peace be upon him) who had come up behind caught me by the back of the neck, and when I looked at him he was laughing. He said: Go where I ordered you, little Anas. I replied: Yes, I am going, Apostle of Allah! Anas said: I swear by Allah, I served him for seven or nine years, and he never said to me about a thing which I had done: Why did you do such and such? Nor about a thing which I left: why did not do such and such?
Sunan Abi Dawud, Book 43, Hadith 1