Dear Dmytro,
> adukkhamasukhaa upekkhaasatipaarisuddhim catuttha.m jhaanaaa
> upasampajja viharati.
>
The term upekkhaasatipaarisuddhim is somewhat pblematic. The commentators
understand it to means that satipaarisuddhi.m is generated by upekkhaa. Now
suttanipaata 1107 reads upekhaasatisa.msuddha.m which the Niddesa
understands to mean purity of upekkhaa and sati (upekkhaa ca sati ca suddhaa
honti). The two terms are evidently related It seems to me that this old
understanding of the term - possibly older than the interpretation found in
the Vibha.nga - should betaken into consideration, when discussing the
nature of the mental state this term describes, it is, as we know, used in
the context of the forth jhaana.
Best regards,
Ole Pind