Upekkhāvihārissa pana ‘‘sattā sukhitā vā hontu dukkhato vā vimuccantu, sampattasukhato vā mā vimuccantū’’ti ābhogābhāvato sukhadukkhādiparamatthagāhavimukhabhāvato avijjamānaggahaṇadukkhaṃ cittaṃ hoti.
Ñ(IX,123): When he abides in equanimity, his mind becomes skilled in apprehending what is (in the ultimate sense) non-existent, because his mind has been diverted from apprehension of (what is existent in) the ultimate sense, namely, pleasure, (release from) pain, etc., owing to having no further concern such as 'May beings be happy' or 'May they be released from pain' or 'May they not lose the success they have obtained'.
Athassa paramatthagāhato vimukhabhāvaparicitacittassa paramatthato avijjamānaggahaṇadukkhacittassa ca anukkamādhigataṃ viññāṇañcāyatanaṃ samatikkamma sabhāvato avijjamāne paramatthabhūtassa viññāṇassa abhāve cittaṃ upasaṃharato appakasireneva tattha cittaṃ pakkhandati.
Ñ: Now his mind has become used to being diverted from apprehension of (what is existent in) the ultimate sense, and his mind has become skilled in apprehending what is non-existent in the ultimate sense, (that is to say, living beings, which are a concept), and so when he surmounts the base consisting of boundless consciousness attained in due course and applies his mind to the absence, which is non-existent as to individual essence, of consciousness, which is a reality (is become—see M.i,260) in the ultimate sense, then his mind enters into that (nothingness, that non-existence) without difficulty (see Ch. X, §32).
Iti upekkhā ākiñcaññāyatanassa upanissayo hoti, na tato paraṃ,
Ñ: So equanimity is the basic support for the base consisting of nothingness, but not for what is beyond that.
tasmā ākiñcaññāyatanaparamāti vuttāti.
Ñ: That is why it is called 'having the base consisting of nothingness as the highest'.