It says in Pirkei Avos "מורא רבך כמורא שמים" - Simply, your fear of your Rebbi should be like your fear of Hashem.
Reb Eizekel of Zidichov explained - Your fear of your Rebbi should be like HIS fear of Hashem.
The Rebbe Shlita related that he was once walking with the Holy Beis Yisrael in Bayit Ve-gan and their were children who were playing in the sidewalk. Suddenly one of the children saw the glowing countenance of the Beis Yisrael and cried out "Immmmmaaaa-leeeeeeee" and ran away to his mother. The Beis Yisrael couldn't understand why he scared the child away.
What happened, explained the Rebbe Shlita, is that this child's neshama sensed that there was an intense amount of kedusha in this holy man.
[From a drasha given motzei shabbos parshas Va-eschanan 5774]