He who has knowledge And Won't Freely Share It Is Called What

He sits in silence, his words held tight, A well of wisdom, sealed from sight. His lips are firm, his eyes withdrawn, As night falls silent before the dawn. The world is thirsty, tongues run dry, Yet he keeps still, lets truth pass by. A lantern dimmed, a book unread, His world's are lost in the wind instead. He knows the path but guards the way, Locks the door, throws the key away. His heart is hollow, his soul a tomb, A candle smothered, a rose in gloom. In shadows he lingers, world's fade in the air, He who has knowledge and won't freely share it, Is what?