When a bell is struck it rings, when a drum is beaten it resounds. This is because they are solid outside and empty within. It is because they have nothing inside that they are able to ring and resound.
What I realize as I observe this is the Tao of true emptiness and ineffable existence.
True emptiness is like the inner openness of a bell or a drum; ineffable existence is like the sounding of a bell or a drum when struck. If people can keep this true emptiness as their essence, and utilize this ineffable existence as their function, ever serene yet ever responsive, ever responsive yet ever serene, tranquil and unstirring yet sensitive and effective, sensitive and effective yet tranquil and unstirring, empty yet not empty, not empty yet empty, aware and efficient, lively and active, refining everything in the great furnace of Creation, then when the dirt is gone the mirror is clear, when the clouds disperse the moon appears; revealing the indestructible body of reality, they transcend yin and yang and Creation, and merge with the eternity of space.
― Liu Yiming, Awakening to the Tao