Mahabharat
न चातिधैर्येण चरेद गुरुतां हि वरजेत तथा समितं तु मृदुपूर्वेण दर्शयेत परसादजम ॥ ४-४-३० ॥
'Nor should one conduct himself with excessive gravity, for that too may appear arrogant. Instead, let him display a gentle smile, showing his goodwill with softness and humility.' ॥ 4-4-30 ॥
english translation
na cAtidhairyeNa careda gurutAM hi varajeta tathA samitaM tu mRdupUrveNa darzayeta parasAdajama ॥ 4-4-30 ॥
hk transliteration by Sanscript