Comm. NT: 68.
Ānāpānassatikathāvaṇṇanā
“The act of relinquishing as the act of giving up by means of substituting for what should be abandoned its opposite quality or by cutting it off, is ‘relinquishment as giving up.’
Likewise the act of relinquishing of self that takes place in non-formation of kamma, which is the relinquishing of all substrata (circumstances) of becoming, being the entering into that [Nibbāna] either by inclination towards it [in insight] or by having it as object [in the path] is ‘relinquishment as entering into.’
‘Through substitution of opposite qualities’: here contemplation of impermanence, firstly, gives up perception of permanence by abandoning through substitution of the opposite [e.g. substituting perception of impermanence for that of permanence in the case of all formed things]. And the giving up in this way is in the form of inducing non-occurrence. For all kamma-formations that are rooted in defilements due to apprehending (formations) as permanent, and the kamma-resultant aggregates rooted in both which might arise in the future, are abandoned by causing their non-occurrence. Likewise in the case of perception of pain, and so on.
‘Through seeing the wretchedness of what is formed’: through seeing the fault of impermanence, etc., in the formed three-plane field of formations.
It is ‘the opposite of the formed’ owing to its permanence, and so on.
The word pakkhandana (rendered by “entering into”) is used to define the act of faith, and can also be rendered by “launching out into” or by “leap.”