The Heart Sutra lists three groups of non-duality (of course not limited to three) to illustrate the reality character of all Dharmas - emptiness. The noumenon of all Dharma or one's own nature is neither arising nor ceasing, neither pure nor impure and neither increasing nor decreasing.
With respect to existence, as emptiness character has no beginning in the past, there is no birth, nor production, nor arising. As emptiness character has no end in the future, there is no death, nor extinction, nor ceasing.
With respect to quality, pureness and impureness are duality and relative to each other. Its existence depends on each other. There is no absolute pureness nor absolute impureness/defilement.
With respect to quantity, it is a constant without increasing or diminishing.
It is also known as Middle Way, another profound doctrine in Buddhism.