allah, the exalted, says:

"enjoin you al-birr (piety and righteousness and every act of obedience to allah) on the people and you forget (to practise it) yourselves, while you recite the scripture [the taurat (torah)]! have you then no sense?". (2:44)

"o you who believe! why do you say that which you do not do? most hateful it is with allah that you say that which you do not do". (61:2,3)

"(shu`aib said:) i wish not, in contradiction to you, to do that which i forbid you.'' (11:88)

198. usamah bin zaid (may allah bepleased with them) reported: messenger of allah (pbuh) said, "a man will be brought on the day of resurrection and will be cast into hell, and his intestines will pour forth and he will go round them as a donkey goes round a millstone. the inmates of hell will gather round him and say: `what has happened to you, o so-and-so? were you not enjoining us to do good and forbidding us to do evil?' he will reply: `i was enjoining you to do good, but was not doing it myself; and i was forbidding you to do evil, but was doing it myself".
[al-bukhari and muslim].

commentary: this hadith serves a stern warning for such `ulama', preachers and reformers of the ummah whose own conduct is contrary to the sermons they give from the pulpit.