《老子·道经·第十五章》
古时候在修道方面有造诣的人，微妙通达，深刻玄远，不是一般人可以理解的。
古之善为士者，微妙玄通，深不可识。
In ancient times, those who made great achievements in Taoist cultivation were subtle, penetrating, and profound, so average people found it impossible to understand them.