Sahih Muslim Book 42, Hadith Number 7122.

Chapter : The Punishment of one who Commands others to do good but does not do it himself and he forbids others to do evil but does not himself refrain from it.

Shaqiq reported that it was said to Usama b. Zaid: Why don’t you visit ‘Uthman and talk to him? Thereupon he said: Do you think that I have not talked to him but that I have made you hear? By Allah. I have talked to him (about things) concerning me and him and I did not like to divulge those things about which I had to take the initiative and I do not say to my ruler: “You are the best among people,” after I beard Allah’s Messenger (may peace be upon him) as saying: A man will be brought on the Day of Resurrection and thrown in Hell-Fire and his intestines will pour forth in Hell and he will go round along with them, as an ass goes round the mill-stone. The denizens of Hell would gather round him and say: O, so and so, what has happened to you? Were you not enjoining us to do what was reputable and forbid us to do what was disreputable? He will say: Of course, it is so; I used to enjoin (upon people) to do what was reputable but did not practise that myself. I had been forbidding people to do what was disreputable, but practised it myself.