As for the scholars of mathematics, physics, chemistry and astronomy, people only take from them their expertise and do not ask them about their way of life.  However, as for the scholar of the religion, if his way of life is separate from his speech, his call to Allah U will fall that is, fail. Just as a poet has said,

        “Oh One who teaches others!

          Be wary over yourself the one who is educating,

          You prescribe medication to the one of illness and weakness,

          How can they ever get better when you yourself are sick?”

So, whoever goes up a rostrum and warn people against backbiting and gives Qur’anic proofs and recites Allah’s U word:

﴾أَيُحِبُّ أَحَدُكُمْ أَن يَأْكُلَ لَحْمَ أَخِيهِ مَيْتًا فَكَرِهْتُمُوهُ﴿

“Would one of you like to eat the flesh of his brother when dead? You would detest it.” [Surah Al-Hujurat: 12],