坐禪三昧經 1.12

1.12

If one is attached to a pure body, one should also be attached to a foul, rotting body; if one is not attached to a foul body, one should likewise not be attached to a pure body, because the two bodies are equal. If one seeks the reality of both, purity is equally unobtainable in either. The minds of humans are mad and confused, covered over by inverted views, taking the impure to be pure. If the inverted mind is broken, one then attains the contemplation of the true mark of dharmas, and realizes that impurity is deceptive and unreal. Furthermore, a dead corpse is without fire, without life, without consciousness, and without the sense faculties; knowing this clearly, human minds do not give rise to attachment to it. Because [a living] body has warmth, has life, has consciousness, and has complete sense faculties, the mind becomes inverted, confused, and attached. Furthermore, when the mind is attached to bodily form, it deems it pure; once the mind of attachment ceases, it realizes it is impure. If it were truly pure, it ought to be permanently pure, but now that is not so. Just as a dog eating feces considers it pure, but viewed by humans it is extremely impure, so too within and outside this body there is not a single pure spot. If one is attached to the exterior of the body: taking the thin outer skin from the entire body, it barely amounts to the size of a crabapple, and that too is impure—how much more so the thirty-six substances inside the body! Furthermore, examining the causes and conditions of the body, they are impure in many ways: it is formed from the impure union of the parents' semen and blood; once it has become a body, it constantly discharges impurities; clothing, bedding, and mats also become foul and impure—how much more so at the place of death! By this one should know that within saṃsāra, inside and out, all is impure. (From here below in the sūtra text to the beginning of the second door.)